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THE  subject  with  which  this  book  is  concerned  is  one 
of  vast  extent  and  enormous  importance.  It  covers 
wide  tracts  of  territory  in  physiology  and  medicine. 
"  All  life  processes,"  as  Prof.  Wolfgang  Ostwald  has 
summarily  said,  "  take  place  in  a  colloidal  system," 
and  that  is  true  both  of  the  normal  fluids  and  secretions 
of  the  organism  and  of  the  bacterial  toxins,  as  well  as, 
in  large  measure,  of  the  reactions  which  confer  im- 
munity. If  this  is  so,  it  would  seem  to  be  an  obvious 
desideratum  that  the  drugs  employed  to  combat  disease 
should  be  in  the  colloidal  state,  i.e.  in  a  form  in  which 
they  may  be  isomorphic  and  isotonic  with  the  elements 
of  the  body.  Only  so  can  they  be  expected  to  exert 
their  full  potency.  The  task  of  thus  bringing  their 
remedial  virtue  to  its  highest  point  is  not  an  easy 
one,  for  colloidal  substances,  unless  prepared  with 
consummate  skill  and  meticulous  care,  lack  stability, 
and  are  prone  to  precipitation  when  brought  into 
contact  with  the  electrolytes  normally  present  in  the 
body  tissues  and  fluids.  That  it  is  not  beyond  the 
resources  of  scientific  chemistry  is  clearly  shown  in 
this  book.  A  measure  of  success  has,  in  fact,  been 
achieved  which  leaves  no  doubt  of  the  brilliant  future 
which  lies  before  drugs  in  the  colloidal  form. 
To  the  study  of  colloids,  both  in  health  and  disease, 


some  of  the  world's  greatest  investigators  have  devoted 
and  are  devoting  their  genius  for  research.  Much  that 
was  mystery  has  already  been  elucidated.  A  very 
considerable  body  of  literature  has  accumulated,  and 
the  time  is  ripe  for  such  lucid  expositions  of  ascer- 
tained results  as  will  be  found  in  these  pages,  written 
by  an  acknowledged  master  of  the  subject. 


THE  present  volume  is  based  on  a  lecture  delivered  at 
the  request  of  the  Chadwick  Trustees,  under  the  chair- 
manship of  Sir  William  Collins,  K.C.V.O.,  and  forms  one 
of  a  series  of  works  published  under  their  auspices. 
Some  of  the  information  also  appears  in  the  author's 
contribution  to  the  British  Association  Report  on 
Colloids,  viz.  The  Administration  of  Colloids  in  Disease, 
published  by  the  Department  of  Scientific  and  Indus- 
trial Research,  and  obtainable  from  H.M.  Stationery 


A.  B.  SEARLE. 


November,   1919. 


FOREWORD         ......... 

AUTHOR'S  NOTE         ........ 

OF  COLLOIDS  ....... 



WATER — SOAPS  ...... 



VI.     USE  OF  COLLOIDS  IN  MEDICINE       .... 

NUMBER  .  .  



X.    CONCLUSION  ....... 













THE  difference  between  a  healthy  and  a  diseased 
organism  is  so  important,  and  the  necessity  for  im- 
proving the  health  of  the  nation  is  so  urgent,  that  any 
application  of  knowledge  to  this  end  is  worth  very  serious 
consideration.  Consequently  it  is  necessary  that  any 
possible  use  of  discoveries  in  branches  of  science, 
other  than  medicine,  should  be  brought  to  the  atten- 
tion of  all  concerned  with  the  least  possible  delay. 
This  application  of  knowledge  gained  in  various  fields 
of  investigation  to  the  improvement  of  health  and  the 
reduction  of  disease  was  one  of  the  foundation  prin- 
ciples of  Sir  Edwin  Chadwick,  whose  generosity  made 
the  present  publication  possible. 

The  study  of  hygiene  and  of  many  diseases  has  been 
enormously  facilitated  by  the  discovery  that  many  of 
the  ills  that  flesh  is  heir  to,  and  many  others  which  it 
is  unnecessary  to  suffer,  are  due  to  the  influence  of 
bacteria  and  their  products.  There  is,  however,  a 
still  wider  cause  of  disease,  of  which  bacteria  form 
only  a  part,  which  is  due  to  the  peculiar  structure  of 
the  essential  organs  of  all  animals  and  vegetables — a. 


structure  which  has  long  been  recognised  in  certain 
ways,  though  some  of  its  properties  have  only  been 
realised  within  the  last  decade  or  two. 

We  are  all  aware  that  living  organisms  are  com- 
posed of  a  number  of  cells  consisting  of  an  external 
envelope,  or  membrane,  and  an  enclosed  fluid.  Even 
the  most  complex  animal  structure  can  be  shown  to 
consist  of  a  vast  number  of  such  cells,  differing  enor- 
mously in  their  shape  and  functions,  but  all  possessing 
certain  well-defined  characteristics.  The  membranes 
or  envelopes  of  these  cells  possess  the  peculiar  property 
of  allowing  certain  substances  to  pass  through  them 
quite  readily  whilst  others  cannot  do  so,  and  on  this 
property  depend  many  of  the  most  complex  functions 
of  the  whole  organism.  The  processes  of  digestion  and 
assimilation  and  the  oxygenation  of  the  blood  are 
well-known  examples  of  the  selective  passage  of  certain 
substances  through  the  membranes  concerned.  Some 
investigators,  including  Moore  and  Roaf,1  do  not 
accept  the  idea  of  membranes  of  selective  permeability, 
but  consider  the  phenomena  usually  attributed  to 
them  as  being  due  to  selective  absorption.  This 
appears  to  be  specially  applicable  to  living  cells,  as 
several  colloids  behave  differently  in  these  from  what 
they  do  in  synthetic,  or  "  dead,"  membranes. 

It  is  well  known  that  if  a  mixture  of  sand,  gelatin, 
salt,  and  water  were  to  be  filtered  through  cotton  wool, 
paper,  or  other  recognised  filtering  medium,  the  sand 
would  remain  on  the  filter,  but  the  salt  and  gelatin 
would  pass  through  in  solution  in  the  water.  It  is  not 

1  Hober,  Arch.  ges.  Physiol.,  1913,  150,  15  ;  Moore  and  Roaf, 
Roll.  Zeits.,  1913,  13,  133, 


so  well  known  that  if  such  a  solution  of  salt  and 
gelatin  is  placed  in  a  parchment  or  collodion  cup,  and 
the  latter  partially  immersed  in  a  vessel  of  water,  the 
salt  will  pass  into  the  water,  but  the  gelatin  will 
remain  behind  in  the  cup.  By  repeatedly  changing 
the  water  in  the  outer  vessel  the  whole  of  the  salt  may 
be  removed  from  the  gelatin  solution.  This  distinctive 
property  of  salt  and  gelatin  was  investigated  by 
Thomas  Graham,  who  found  that  all  those  substances 
which  pass  readily  through  a  filter,  but  not  through  a 
membrane,  had  certain  other  resemblances.  He  also 
found  that  some  substances  could  exist  in  such  a  state 
that  they  would  pass  either  through  a  membrane  or 
not,  according  to  their  method  of  preparation.  Fara- 
day extended  this  investigation,  prepared  a  number 
of  substances  in  this  state,  and  found  that  they  had 
properties  quite  different  from  those  ordinarily  pos- 
sessed by  them.  Thus,  metallic  gold,  which  is  peculiarly 
insoluble  and  resistant,  could  be  obtained  in  so  fine  a 
state  of  suspension  that  it  passed  readily  through  all 
ordinary  filters  and  behaved  as  a  solution.  At  the 
same  time  its  colour  was  entirely  different  from  that 
characteristic  of  the  metal,  being  red  or  blue  instead 
of  yellow,  and  its  other  properties  were  changed  to  a 
correspondingly  great  extent. 

When  Thomas  Graham,  in  1861,  found  that  certain 
solutions  would  pass  through  a  membrane,  whilst 
others  did  not  do  so,  he  little  realised  how  great  a 
discovery  he  had  made.  He  had,  in  fact,  found,  and 
was  able  to  describe,  a  state  of  matter  of  which  little 
or  nothing  was  realised  at  the  time,  though  many 
industries,  and  indeed  life  itself,  were  and  are  dependent 


on  it.  Graham's  chief  discovery  in  this  connection 
was  that  substances  may  enter  into  solution  in  such 
a  manner  that  they  exhibit  characteristics  which  are 
quite  different  from  those  of  a  true  solution.  To  this 
intermediate  state  he  applied  the  term  "  colloidal  " 
(from  Kolla=g\ue),  as  glue,  gelatin,  and  allied  sub- 
stances were  most  readily  recognised  by  him  as  being 
in  the  colloidal  state.  Since  Graham's  time  it  has  been 
found  that  most  substances  can  be  obtained  in  the 
colloidal  state,  their  occurrence  being  sometimes  due 
to  reactions  which  are  specially  characteristic  of 
animal  or  vegetable  organisms  and  sometimes  to 
purely  inorganic  changes. 

The  colloidal  state  may  be  defined  as  a  physical 
condition  of  matter  consisting  of  at  least  two  parts  or 
phases,  one  of  which  is  the  active  substance  and  the 
other  the  one  in  which  it  is  distributed.  The  former 
is  termed  the  disperse  phase  ;  it  is  the  active  agent  and 
may  consist  of  either  solid  or  liquid  particles  which  are 
so  minute  that  they  remain  for  an  indefinitely  long 
period  in  suspension.  The  second  phase  is  either  a 
liquid  or  an  otherwise  homogeneous  complex  material ; 
it  is  known  as  the  dispersion  medium.  Such  a  definition 
does  not,  however,  give  any  clue  to  the  peculiar  pro- 
perties of  substances  when  in  the  colloidal  state,  and 
it  might  be  applied  with  accuracy  to  any  turbid  fluid. 
In  a  colloidal  solution — which  not  being  a  true  solution 
is  preferably  termed  a  sol — the  dispersed  substance  is 
able  to  react  in  a  manner  quite  different  from  what 
would  ordinarily  be  anticipated.  The  dispersed  or 
suspended  particles  are  not  merely  so  minute  tHat  the 
effect  of  gravity  on  them  is  counterbalanced  by  other 


forces  which  keep  them  in  suspension  (though  they 
are  often  only  one-thousandth  part  of  the  size  of 
average  bacteria),  but  they  are  in  a  state  of  unordered 
oscillation  which  gives  rise  to  the  well-known  Brownian 
movement.  They  behave  in  a  liquid  in  a  manner  very 

a.  Hydrogen  molecules.  b.  Chloroform  molecules. 

c.  Haemoglobin  molecules.         d?>  £,/,£'•  Par  tides  of  colloidal  gold. 
h  (large  circle).    Particles  which  precipitate  from  gold  suspensions. 


(Scale  i  :  1,000,000) 

similar  to  the  molecules  and  atoms  of  a  gas,  and  are  in 
constant  movement,  travelling  at  a  high  velocity  and 
repeatedly  colliding  with  each  other.  There  is  no 
group  of  substances  which  are  invariably  colloids. 
Thus  soaps  dissolve  in  alcohol  and  behave  as  true 


crystalloids  ;  in  water  they  behave  equally  character- 
istically as  colloids.  Common  salt,  on  the  contrary, 
behaves  as  a  colloid  in  relation  to  benzole,  but  as  a 
crystalloid  when  dissolved  in  water.  Von  Weimarn 
and  others  have  shown  that  so  many  substances  can 
be  obtained  in  the  form  of  colloidal  solutions  that  it  is 
probably  correct  to  regard  colloids  as  substances  which 
are  in  a  particular  state  rather  than  as  forming  a 
distinct  group  of  substances.  Colloids  are  readily 
divisible  into  two  fairly  well-defined  groups  to  which 
various  names  have  been  given  by  different  investi- 
gators, the  most  generally  accepted  being  emulsoid 
(fluid  particles)  and  suspensoid  (solid  particles),  as 
suggested  by  Wo.  Ostwald.  The  colloids  in  the  first 
group  have  many  of  the  properties  of  gelatin  or  glue  ; 
they  swell  when  immersed  in  a  suitable  fluid  (water), 
absorbing  a  large  quantity  of  it,  and  gradually  become 
so  dispersed  as  to  possess  many  of  the  properties  of  a 
solution.  The  apparently  solid  particles  have  many  of 
the  properties  of  a  liquid,  and  for  this  reason  the  term 
emulsoid  is  very  aptly  applied  to  them.  The  behaviour 
of  emulsoids  towards  electrolytes  is  so  complex  that 
their  classification  on  an  adequate,  yet  simple,  scale 
is,  at  present,  impossible.  The  second  group  of 
colloids  contains  substances  which  are  much  more 
sensitive  to  small  traces  of  added  substances,  and  the 
electric  charge  acquired  by  them  is  much  greater. 
They  appear  to  consist  of  extremely  minute  particles 
of  solid  matter,  though  this  adjective  must  not  be 
applied  too  rigidly  in  this  connection. 

There    are    many   well-known    organic   substances 
which    occupy    an    intermediate    position    between 


colloids  and  crystalloids,  and  are  conveniently  termed 
semi-colloids.  Casein,  soap,  many  degradation  pro- 
ducts of  albumen,  peptones,  and  other  constituents  of 
animal  organisms,  and  several  dyes  belong  to  this 
class.  Thus  albumen  is  a  true  emulsoid,  but  the  pro- 
talbic  and  lysalbic  acids  derived  from  it  diffuse  through 
the  parchment  and  behave  in  other  ways  as  crystal- 
loids, whilst  at  the  same  time  having  several  properties 
(such  as  opalescence,  viscosity,  and  "  protective 
action  ")  which  are  characteristics  of  colloids.  Semi- 
colloids,  such  as  soaps,  may  not  be  colloids  under 
ordinary  conditions,  but  form  colloidal  sols  when  in 
contact  with  certain  liquids ;  they  are  sometimes 
termed  colloidogens.  Other  semi-colloids  are  clearly 
electrolytes,  but  their  boiling  points  and  vapour  pres- 
sures are  approximately  the  same  as  those  of  water ; 
these  and  other  properties  are  so  abnormal  that  such 
substances  must  be  classed  among  the  semi-colloids. 

Each  colloidal  particle  also  carries  a  characteristic 
definite  charge  of  electricity,  some  colloids  being 
electro-positive  and  others  electro-negative.  Usually, 
when  any  given  substance  is  in  the  colloidal  state  it 
has  the  same  electric  sign,  but  by  adopting  special 
methods  of  preparation  it  is  possible  to  produce  some 
substances  in  a  colloidal  form  in  which  the  particles 
may  have  either  a  positive  or  a  negative  electric 
charge.  The  electrification  of  colloidal  particles  may 
be  compared  with  that  of  a  piece  of  glass  suspended  by 
a  thin  silk  thread  and  rubbed  with  a  piece  of  amal- 
gamated silk.  If  a  second  piece  of  glass  similarly 
electrified  by  rubbing  is  brought  near  to  the  first  there 
will  be  a  mutual  repulsion.  On  the  other  hand,  a 


piece  of  ebonite  which  has  been  rubbed  with  fur  will 
attract  the  glass  because  it  carries  an  electric  charge 
of  the  opposite  sign.  The  electric  charge  is  not  the 
total  amount  of  electricity  which  the  body  possesses, 
but  only  the  excess  or  deficit  of  that  which  it  carries 
compared  with  the  neutral  electrical  condition. 

It  is  important  to  note  also  that  the  chemical  com- 
position, and  often  the  physical  appearance  of  a  sub- 
stance, gives  no  indication  of  the  electric  charge  which 
it  has  acquired,  so  that  unless  the  charge  is  definitely 
investigated  its  existence  may  be  overlooked.  This  has 
to  a  large  extent  been  the  case  in  the  study  of  many 
drugs  and  other  remedies. 

Substances  such  as  glass  and  ebonite  are  most  easily 
charged  electrically  as  the  result  of  friction,  but  this 
is  by  no  means  the  only  or  even  the  most  important 
cause  of  excitation.  If  two  different  metals  are 
moistened  and  brought  into  contact,  a  feeble  but  observ- 
able electrification  is  produced.  This  is  easily  shown 
by  holding  a  silver  and  copper  coin  edgewise  on  the 
tongue.  So  long  as  the  coins  are  separate  no  electrifica- 
tion results,  but  directly  they  touch  each  other  at  some 
point  away  from  the  tongue  the  taste  produced  by  the 
electrification  becomes  apparent.  If  two  dissimilar 
metals  are  partially  immersed  in  a  liquid  which  can 
chemically  react  on  one  of  them,  a  simple  voltaic  cell 
or  battery  unit  is  formed,  the  electric  current  pro- 
duced depending  on  the  sizes  of  the  pieces  of  metal 
and  on  the  nature  of  the  fluid  used.  Chemical  action 
and  electric  phenomena  are,  indeed,  so  closely  related 
that  in  many  instances  one  cannot  occur  without  the 
other.  In  fact,  many  phenomena  which  are  generally 


regarded  as  chemical  are  largely  electrical  in  character, 
or  at  least  may  be  helpfully  considered  as  such. 

For  example,  the  dissociation  of  a  compound  into 
its  elements  or  into  two  distinct  groups  of  ions  is 
frequently  accompanied  by  the  assumption  of  definite 
electric  charges  by  each  of  the  groups.  Thus,  when  a 
solution  of  common  salt  in  water  is  made  sufficiently 
dilute,  the  salt  is  dissociated  into  positively  charged 
sodium  and  negatively  charged  chlorine  particles,  or 
ions.  Sulphuric  acid — a  more  complex  substance 
— is  dissociated  into  positive  hydrogen  ions  and 
negative  SO4  ions.  Even  a  partial  dissociation  of  the 
fluid  in  which  the  substance  is  dissolved  or  suspended 
may  cause  the  colloid  to  acquire  an  electric  charge. 
Thus,  water  (H+-OH~)  can  form  two  classes  of  colloids 
the  particles  of  which  are  respectively  positively  and 
negatively  charged,  and  it  is  suggested  that  in  many 
cases  there  is  a  chemical  combination  with  the  liquid 

aPt+H+-OH-  =  (Pt.H+)+OH-, 

aPb+H+'OH-  =  (Pb,OH-)+H+. 

The  charge  on  a  sol  is  very  much  less  than  on  an 
equivalent  amount  of  the  corresponding  ion,  and, 
therefore,  a  larger  amount  of  sol  will  be  required  when 
it  is  used  as  a  reagent. 

Burton  has  estimated  a  charge  for  a  single  particle 
of  gold  and  silver  sols  on  the  assumption  that  the 
amount  of  Al  in  aluminium  salts  which  just  precipi- 
tates the  gold  or  silver  has  acquired  the  same  amount 
of  positive  electricity  as  that  amount  of  negative 
electricity  acquired  by  the  precipitated  particles. 

The  volume  of  a  particle  is  2Xio~4  cc.,  so  that 


100  cc.  of  a  sol  with  6-5  mgms.  silver  contains  3  x  io10 
particles.  This  volume  of  sol  required  3-oxio~5 
and  2-6xio~5  gms.  of  A12(SO4)3  for  precipitation, 
from  which  the  charge  on  a  particle  is  2-8xio~2 
electrostatic  units,  and  the  charge  on  one  gram-equiva- 
lent of  silver  in  a  sol  is  4  per  cent  of  the  charge  on  one 
gram-equivalent  of  silver  ion.  This  dissociation  on 
solution  with  the  assumption  of  an  electric  charge  is 
well  known  to  chemists,  though  it  is  not  so  obvious 
to  others  on  account  of  the  minuteness  of  the  particles 
and  of  the  charges  which  they  carry.  There  is  a 
general  agreement  among  those  who  have  studied  the 
subject  that  colloidal  sol  particles  are  enclosed  by  a 
double  electric  layer,  as  suggested  by  Quincke  and 
Helmholtz  ;  when  a  particle  is  negatively  charged 
there  is  a  negatively  electrified  layer  on  its  surface, 
whilst  in  the  liquid  immediately  surrounding  the 
particle  is  a  corresponding  layer  which  is  charged 
positively.  Burton  has  shown  that  there  is  a  layer  of 
hydroxide,  or  hydride,  on  the  colloidal  metals  which 
may  affect  the  external  change  on  these  sols.  It  is 
not  definitely  known  how  this  double  layer  is  formed, 
and  for  most  purposes  it  is  sufficient  to  regard  the 
particles  as  positively  or  negatively  charged,  the 
effect  of  the  double  layer  being  neglected. 

Any  substance  which  conducts  an  electric  current, 
and  is  decomposed  thereby  into  separate  groups  of 
ions,  is  known  as  an  electrolyte.  The  terminals,  or 
plates,  by  which  the  current  is  passed  through  a  liquid 
are  known  as  electrodes,  the  one  by  which  the  current 
is  supposed  to  enter  being  termed  the  positive  (-J-) 
electrode,  or  anode,  and  the  other,  the  negative  (— ) 


electrode,  or  kathode.  When  a  current  of  electricity 
is  passed  through  the  solution  the  positively  and 
negatively  charged  groups  tend  to  collect  at  the 
opposite  ends  of  the  solution,  i.e.  they  tend  to  travel 
to  each  electrode  respectively,  and  are  in  this  way 
separated  from  each  other,  though  they  lose  their 
characteristic  charge  as  soon  as  they  come  into  con- 
tact with  the  electrode.  Thus,  if  a  current  of  electricity 
is  passed  through  water  containing  sufficient  acid  to 
render  it  a  conductor,  the  oxygen  atoms  will  pass  to 
the  anode  and  the  hydrogen  to  the  kathode,  each 
escaping  from  the  solution  in  the  form  of  a  gas  without 
any  electric  charge.  Between  the  electrodes,  however, 
the  oxygen  ions  have  their  distinctive  charges  and  are 
able  thereby  to  act  very  differently  from  the  electrically 
neutral  gases  bearing  the  same  names.  When  a  liquid 
is  contained  in  a  porous  vessel  or  membrane,  which  is 
partially  immersed  in  a  second  liquid,  and  a  current 
is  passed  from  one  liquid  to  the  other,  the  membrane 
plays  an  important  part.  It  prevents  the  liquids  from 
mixing  rapidly,  whilst  it  allows  them  to  come  into 
contact  with  each  other,  so  that  by  arranging  the 
electric  current  to  pass  in  a  suitable  direction  one  sub- 
stance may  be  passed  through  the  membrane  and  thus 
separated  more  rapidly  than  by  the  slow  process  of 
unaided  dialysis  or  diffusion,  whilst  its  separation  from 
other  substances  in  solution  is  effected  more  easily 
and  with  less  general  disturbance  than  if  purely 
chemical  methods  are  used.  The  chief  investigations 
of  the  movements  of  colloidal  particles  under  the  in- 
fluence of  an  electric  current  are  based  on  the  work  of 


Linder  and  Picton,1  who  with  other  observers  have 
found  that  the  substances  mentioned  in  Table  I 
move  to  either  the  positive  or  the  negative  electrode, 
as  shown,  when  suspended  in  pure  water.  In  dilute 
solutions  of  salts,  alkalies,  or  acids,  entirely  different 
characteristics  may  be  observed  with  the  same  colloidal 

Thus,  some  colloids  such  as  globulin  and  silicic  acid 
are  negatively  charged  in  alkaline  solutions  and  posi- 
tively charged  in  acid  solutions. 




(negatively  charged  and  mov- 
ing to  the  positive  pole) 

Antimony  sulphide 
Arsenic  sulphide 
Cadmium  sulphide 
Platinum  sol 
Silver  sol 
Gold  sol 
Mercury  sol 
Silver  chloride 
Silver  bromide 
Silver  iodide 
Vanadic  oxide 
Tin  oxide 

Aniline  blue 

Molybdene  blue 
Soluble  Prussian  blue 

(positively  charged  and  mov- 
ing to  the  negative  pole) 

Hydroxides  of 

Iron,  Chromium 
Copper,  Aluminium 
Zirconium,  Cerium 
Bredig  sols  of 

Bismuth,  Lead 
Iron,  Copper 
Hoffmann  violet 
Magdalene  red 
Methyl  violet 
Rosaniline  hydrochloride 
Bismarck  brown 
Methylene  blue 
Titanic  oxide 

1  Journ.  Chem.  Soc.,  61,  148  ;  87,  63  ;  71,  568  ;  87,  1906. 



(negatively  charged  and  mov-  (positively  charged  and  mov- 

ing to  the  positive  pole)  ing  to  the  negative  pole) 

Fuchsine  Diatoms 

Iodine  Unicellular  algae 

Sulphur  Vegetable  organisms 

Oil  emulsions 
Amoeba?  and  animal 

The  electric  charges  on  gelatin,  agar,  and  silicic  acid  are 
very  small  and  difficult  to  observe. 

The  rate  of  movement  of  a  particle  in  an  electric 
field  is  independent  of  the  size  of  the  particle,  but  is 
affected  by  the  viscosity  of  the  fluid  and  the  potential 
of  the  current. 

The  employment  of  electricity  remedially  for  effect- 
ing the  movement  of  the  colloidal  substances  in  the 
living  cells  is,  however,  extremely  limited,  especially 
with  regard  to  animal  organisms,  as  a  separate  elec- 
trode would  require  to  be  introduced  into  each  indi- 
vidual cell — a  hopelessly  impracticable  condition. 
The  result  of  applying  an  electric  current  to  a  large 
area  is  entirely  different  from  that  which  occurs  during 
the  electrolysis  of  a  single  cell.  When  two  sols  of  the 
same  sign  are  mixed  they  not  only  do  not  precipitate 


each  other,  but  the  mixed  sol  acquires  the  stability  of 
the  more  stable  component.  No  adequate  explanation 
of  this  fact  has  yet  been  published,  though  the  fact 
itself  is  indisputable.  When  two  particles  of  opposite 
sign  come  within  a  suitable  distance  of  each  other  they 
are  mutually  attracted  and,  if  sufficiently  free,  will 
eventually  touch  and  discharge  each  other.  The 
product  will  then  be  electrically  neutral  unless  one  of 
the  particles  carries  a  larger  charge  than  the  other, 
when  the  product  will  carry  the  balance  of  the  charge 
or  will  decompose,  forming  an  electrically  neutral 
substance — which  settles  more  or  less  rapidly — and  a 
negatively  charged  product. 

Substances  in  the  colloidal  sol  state  have  correspond- 
ing electric  charges  and  therein  bear  a  very  close 
resemblance  to  substances  which  become  ionised  in 
solution.  They  attract  particles  of  opposite  sign  and 
repel  those  of  like  sign  which  come  within  the  sphere 
of  their  influence,  and  when  two  colloidal  sol  particles 
of  opposite  sign  come  into  contact  with  each  other 
they  are  mutually  discharged,  and  the  combined  pro- 
duct settles  more  or  less  rapidly.  Thus,  the  effect  of 
discharging  two  colloidal  sol  particles  is  to  remove 
them  from  the  active  colloidal  state  and  to  form  a 
precipitate  or  even  a  coagulum.  This  may,  under  some 
conditions,  retain  a  certain  amount  of  chemical 
activity,  and  being  then  in  an  intermediate  state 
between  a  sol  and  a  precipitate  is  conveniently  known 
as  a  gel.  Gels  are  usually  obtained  when  emulsoid  sols 
are  cooled  or  evaporated  ;  they  may  be  regarded  as 
composed  of  two  liquid  phases,  whereas  a  sol  bears  a 
closer  resemblance  to  a  solid  phase  dispersed  in  a  liquid 


one.  Gels  have  characteristic  optical  properties,  such 
as  double  refraction. 

Agglutination,  or  the  precipitation  of  colloids  of  like 
sign,  occurs  in  some  cases,  e.g.  with  toxins  and  bacteria 
sols.  Though  extensively  used  by  some  pathologists 
as  the  basis  of  treatment  of  diseases  due  to  toxins, 
bacteria,  etc.,  the  precise  nature  of  the  phenomena 
which  produce  agglutination  are  by  no  means  well 
understood.  Lottermoser,  in  1901,  found  that  when  a 
positive  sol  precipitates  a  negative  one,  the  precipitate 
contains  both  colloids. 

The  amount  of  one  sol  required  to  precipitate 
another  varies  with  the  nature  of  the  sols,  and  the 
precipitate  contains  both  colloids,  though,  owing  to 
the  difficulty  of  nitration  without  adsorption,  the 
liability  of  the  excess  of  colloid  in  the  sol  to  precipitate, 
and  the  slowness  of  the  reaction,  it  is  often  difficult 
to  determine  the  amount  of  each  colloid  in  a  precipitate. 

The  equivalent  amount  of  sols  required  to  cause 
precipitation  is  not  a  chemical  equivalent,  but  an 
electrical  one  ;  usually  the  maximum  precipitation 
occurs  when  the  positive  charge  on  one  cell  exactly 
equals  the  negative  charge  on  the  other,  but  the 
number  of  particles,  their  size,  and  the  rate  of  mixing 
affect  the  results. 

Substances  in  colloidal  solution  behave  quite  differ- 
ently from  those  which  are  merely  in  suspension. 
Thus,  coarse  suspensions  are  not  affected  by  electro- 
lytes and  they  do  not  usually  bear  a  definite  electric 
charge,  whereas  colloidal  sols — unless  protected — are 
very  sensitive  even  to  traces  of  electrolytes,  and 
readily  migrate  towards  one  pole  when  an  electric 


current  is  passed  through  them.  It  is  a  mistake  to 
regard  them  merely  as  fine  suspensions,  as  the  proper- 
ties of  a  substance  undergo  considerable  change  when 
it  is  converted  into  the  sol  state.  They  do  not  behave 
precisely  the  same  as  either  suspensions  or  solutions, 
but  occupy  an  intermediate  position  for  which  the 
term  "  sol  "  is  preferable.  It  was  at  one  time  thought 
that  colloidal  substances  could  be  defined  as  those 
which  appeared  to  be  in  suspension  but  do  not  pass 
through  a  parchment  or  collodion  membrane  into  an 
external  volume  of  water.  This  is  by  no  means  always 
the  case,  as  Graham  soon  found,  and  since  his  time 
more  anomalies  have  been  discovered.  It  is  scarcely 
possible,  therefore,  in  simple  terms  to  say  precisely 
which  substances  are  colloidal  and  which  are  not, 
though  for  most  practical  purposes  the  distinction  is 
readily  appreciated.  Like  "  life/'  we  may  have  a  fairly 
clear  concept,  but  cannot  express  it  in  mere  words. 

The  difficulty  of  finding  a  clear  line  of  demarcation 
between  colloidal  and  other  substances  is  greatly 
intensified  when  living  organisms  are  studied,  as 
reactions  take  place  in  these  which  do  not  occur  in  the 
dead  organism.  For  example,  the  peptones  are  a 
class  of  nutritive  substances  which  are  in  many 
respects  typically  colloidal,  and  in  the  laboratory 
their  solutions  do  not  pass  through  animal  or  vegetable 
membranes.  In  the  living  organism,  on  the  contrary, 
peptone  solutions  pass  readily  through  certain  mem- 
branes and  owe  their  nutritive  power  to  this  property. 
Haematin,  on  the  other  hand,  is  a  typical  crystalloid 
substance  which  might  be  expected  to  pass  readily 
through  the  blood  vessels,  yet  it  does  not  do  so  as 


long  as  the  organism  is  alive.  Here  are  two  typical 
substances,  both  acting  precisely  contrary  to  the 
general  behaviour  of  the  groups  to  which  they  belong, 
whilst  in  the  living  organism,  but  behaving  normally 
when  removed  from  the  organism  and  studied  in  vitro. 
This  difference  in  behaviour  impels  all  investigators 
who  are  aware  of  it  to  pause  ere  they  draw  conclusions 
from  laboratory  experiments  and  apply  them  to  the 
living  subject.  Even  in  so  apparently  simple  a 
phenomenon  as  the  passage  of  a  substance  through  a 
membrane,  the  effect  of  "life"  may  be  to  upset  all 
prognostications  from  the  tests  on  dead  or  synthetic 
materials.  This  fact  needs  specially  to  be  borne  in 
mind  when  dealing  with  the  introduction  of  drugs  and 
other  substances  into  the  living  subject,  or  seriously 
erroneous  conclusions  may  be  drawn. 

Turning  again  to  the  characteristics  of  colloidal 
substances,  it  should  be  observed  that  they  are  most 
remarkably  active,  an  apparently  minute  proportion 
of  a  suitable  colloid  frequently  effecting  the  precipita- 
tion of  many  times  its  weight  of  another  substance 
from  "  solution."  In  this  respect,  many  colloids  re- 
semble enzymes,  or  so-called  vegetable  ferments,  and 
bacteria,  though  they  do  not  reproduce  themselves 
like  living  organisms.  They  owe  their  activity  to 
their  minuteness  and  to  the  fact  that  substances  when 
in  the  colloidal  state  have  an  enormous  surface  area 
as  compared  with  their  volume  or  weight,  and  as 
chemical  reactions  depend  on  the  amount  of  contact 
between  two  or  more  particles  these  reactions  will 
proceed  the  more  rapidly  and  completely  when  the 
substances  have  a  large  surface  area  and  are  in  a  state 


of  oscillation.  It  is  well  known  that  chemical  reactions 
can  only  occur  when  two  or  more  substances  are  in 
direct  contact,  and  as  the  completeness  of  the  reaction 
depends  on  the  amount  of  contact,  colloidal  substances 
are  very  powerful  because  of  the  enormous  area  they 

On  the  other  hand,  mass  plays  an  important  part 
in  all  chemical  reactions  and  largely  regulates  their 
intensity.  The  mass  of  colloidal  sol  particles  is  so 
minute  that  the  objectionable  effect  of  intense  reactions 
on  the  human  subject  are  largely  avoided,  whilst  the 
advantages  of  rapid  and  complete  reaction  are  secured. 
For  this  reason,  certain  medicines  administered  in  the 
colloidal  form  are  not  merely  more  active  and  possess 
greater  penetrating  power,  but  they  are  free  from  the 
poisonous  effect  of  the  same  substances  when  given  in 
the  form  of  tincture  or  solution.  The  difference  in 
behaviour  of  a  solution  of  iodine  in  alcohol  or  aqueous 
potassium  iodide,  when  compared  with  that  of  colloidal 
sol  iodine,  is  most  impressive.  The  forms  of  iodine 
usually  employed  induce  pain  and  other  symptoms  of 
iodism,  whereas  large  doses  of  colloidal  sol  iodine  (if 
the  preparation  has  been  properly  prepared)  are  quite 
free  from  this  risk.  A  colloidal  preparation  of  iodine 
in  petroleum  or  other  mineral  oil  can  be  rubbed  into 
the  skin  without  leaving  any  stain,  the  iodine  being 
absorbed  more  readily  than  the  oil.  A  solution  of 
commercial  iodine  in  alcohol  or  in  potassium  iodide 
leaves  a  characteristic  stain  when  applied  to  the 

The  precise  reason  for  this  rapid  absorption  and 
non-staining  action  has  not  been  definitely  ascertained, 


but  it  has  been  repeatedly  demonstrated  in  a  variety 
of  cases. 

The  action  of  radiations  on  sols. — The  y-rays  of 
radium  and  the  X-rays  have  no  action  on  colloidal 
sols.  The  positively  charged  a-rays  of  radium  have 
not  sufficient  penetrating  power  for  any  action  they 
may  have  to  be  important.  The  /3-rays  of  radium, 
which  are  negatively  charged,  hasten  the  coagulation 
of  the  positively  charged  particles  and  increase  the 
stability  of  the  negatively  charged  ones.  A  sample  of 
haemoglobin  was  coagulated  by  the  rays  in  several 
hours  by  Hewin  and  May  en.1  Some  albumen  sols 
when  exposed  to  the  ultra-violet  light  are  rapidly 
coagulated.  These  reactions  partially  explain  some  of 
the  remedial  effects  of  various  radiations  on  the  human 
system.  It  is  clear  that  such  effects  are  limited  by  the 
permeability  of  the  skin,  and  that  for  deep-seated 
affections  better  results  may  be  anticipated  from  the 
introduction  of  suitably  charged  particles  (colloidal 
sols)  into  the  blood  stream. 

The  colour  of  colloids. — The  colour  of  the  colloids 
depends  chiefly  on  the  size  of  the  particles,  and  only 
to  a  small  extent  on  their  composition.  Thus,  the 
smallest  particles  of  colloidal  gold,  when  seen  by 
transmitted  light,  are  red  and  the  larger  ones  are  blue.2 
The  colour  is,  in  each  case,  dependent  chiefly  on  the 
scattering  effect  of  the  particles  on  the  light  trans- 
mitted through  the  liquid.  In  accordance  with 
Rayleigh's  &  Thompson's  calculations,  the  intensity 

1  CR.,  138,  1904,  521  ;  CR.  Soc.  de  Biol,  57,  1904,  33. 
*  Mee  found  the  relation  of  the  size  to  colour  reversed  in  some 


of  the  scattered  light  varies  directly  as  the  sixth  power 
of  the  diameter  of  the  particles  and  inversely  as  the 
fourth  power  of  the  wave-length.  Hence,  the  intensity 
of  the  scattered  light  and  the  absorption  are  both 
greatest  with  the  smallest  particles.  Stebbing  found 
that  very  little  light  leaves  a  colloidal  liquid,  most  of 
it  being  absorbed.  Svedberg  found  that  colloidal  sols 
are  often  more  highly  coloured  than  a  true  solution  of 
the  same  element  at  the  same  concentration,  but  that 
the  absorption  spectra  of  the  colloidal  sols  and  solu- 
tions do  not  differ  essentially.  W.  Ostwald  l  has 
enunciated  the  law  that  "  with  decreasing  size  of  the 
particles  the  absorption  band  of  any  colloidal  solution 
moves  to  the  shorter  wave-lengths." 

Mayer,  Schaffer,  and  Terroine  2  have  shown  that 
traces  of  alkali  increase  the  size  of  the  particles  if  the 
colloid  is  positive,  and  reduce  it  if  the  colloid  is  negative. 
Traces  of  acid  produce  the  reverse  effect.  The  change 
in  the  dispersion  thus  effected  varies  with  the  colour  of 
the  sols.  Zsigmondy3  and  Gutbier  and  Resenschack4 
found  that,  on  adding  coagulating  reagents,  the  colour  of 
gold  sols  changes  consecutively  from  red  to  purple-red, 
red- violet,  blue- violet,  and  deep  blue,  the  colloid 
eventually  separating  as  flakes  of  powder  or  gel. 

1  Roll.  Chem.  Beiheft.,  2,  1910  ;    n,  409. 

2  Comptes  r  endues,  1907,  145,  918. 

3  Zier,  Erkentniss  der  Koll. 

4  Z.f.  anorg.  Chem.,  1904,  39,  112. 



THAT  animal  and  vegetable  fluids  are  largely  colloidal 
in  character  is  a  fact  which  is  now  unquestioned,  but 
little  is  known  as  to  their  precise  nature.  Thus,  the 
particles  in  cow's  milk  can  be  demonstrated  under  the 
ultra-microscope,  but  those  in  human  milk  are  too 
minute.  This  suggests  that  in  adapting  cow's  milk 
for  feeding  infants,  it  is  not  sufficient  to  endeavour  to 
match  the  ordinary  chemical  analysis  of  human  milk, 
but  that  cow's  milk  should  be  treated  in  such  a  manner 
that  the  product  is  in  a  similar  colloidal  state  to  that 
of  the  human  milk.  The  valuable  superiority  for 
infant  use  of  milk  to  which  barley  water,  gruel,  or 
other  starchy  solution  has  been  added  has  long  been 
known,  but  few  have,  as  yet,  realised  that  it  is  due  to 
the  protective  action  (in  a  colloidal  sense)  of  the  added 
substance.  Gelatin,  gum-arabic,  or  preferably  gum- 
acacia,  have  an  even  stronger  protective  action,  and 
they  possess  the  further  advantages  of  being  easier  to 
prepare  and  of  altering  the  composition  of  the  milk  to 
a  less  extent,  whilst  making  it  physically  much  more 
like  human  milk. 

In  human  milk  the  protective  colloid  is  lact-albumen, 
which  is  present  to  the  extent  of  1-3  per  cent  (i.e.  equal 
to  the  casein  present),  whilst  cow's  milk  contains  only 
0-5  per  cent  of  lact-albumen  and  over  3  per  cent  of 



casein.  Of  all  the  domestic  animals,  asses'  milk  bears 
the  closest  resemblance  to  human  milk,  both  in 
chemical  and  colloidal  properties. 

The  coarse  particles  of  curd  which  are  formed  when 
cow's  milk  is  coagulated  by  acids  or  rennet  may  be 
replaced  by  finer,  more  flaky,  and  more  porous  curds 
by  diluting  the  milk  with  water,  by  adding  lime-water 
(though  this  tends  to  prevent  the  coagulation  altogether 
and  so  may  unduly  delay  its  digestion  or  even  cause  it 
to  be  passed  out  of  the  body  of  an  infant  in  the  un- 
digested state),  and  by  the  use  of  one  of  the  protective 
colloids  previously  mentioned. 

Bearing  in  mind  its  colloidal  nature,  human  milk 
can  best  be  imitated  by  using  cow's  milk  as  the  basis 
and  adding  the  following :  (a)  cream  sufficient  to 
raise  the  total  fat  present  to  3-8  per  cent  (about  3  per 
cent  of  the  final  mixture  being  required  usually)  ; 
(b)  milk  sugar  to  raise  the  total  sugar  content  to 
6-2  per  cent  (about  3  per  cent  of  the  total  mixture 
being  usually  required)  ;  (c)  about  I  per  cent  of  lact- 
albumen,  or  2  per  cent  of  gelatin,  or  a  considerably 
larger  percentage  of  starch  in  the  form  of  barley  water, 
etc.,  as  the  protective  colloid ;  and  (d)  sufficient 
water  to  effect  the  solution  of  the  protective  colloid 
and  the  sugar.  If  there  is  any  risk  of  the  cow's  milk 
not  being  quite  fresh,  part  of  the  added  water  may 
wisely  be  replaced  by  a  tablespoonful  of  lime-water, 
which  will  neutralise  any  trace  of  acidity  in  the  milk 
and  will  therefore  increase  its  keeping  power. 

In  the  same  way  chemical  analysis  alone  does  not 
determine  the  value  of  even  the  essential  properties 
of  a  foodstuff ;  its  physical  condition — particularly 


if  it  is  a  colloidal  substance — is  of  at  least  equal  and 
sometimes  greater  importance.  Thus,  cheese  cannot 
be  digested  by  some  people  as  it  is  too  densely  coagu- 
lated to  be  readily  converted  into  a  colloidal  fluid. 
By  preparing  it  under  conditions  which  will  facilitate 
its  resuspension,  its  high  value  as  a  food  material  may 
be  utilised.  The  various  preparations  of  casein  which 
are  at  present  so  popular  as  recuperatives  depend 
largely  on  the  fact  that  they  are  colloidal  substances, 
which  can  be  resuspended  or  converted  into  colloidal 
fluids  more  easily  than  ordinary  cheese  or  dried  milk. 
Indeed,  the  chief  test  of  such  a  preparation  may 
usefully  consist  in  an  examination  of  its  properties 
when  mixed  with  water  or  other  suitable  fluid. 

The  cell-structure  of  animal  and  vegetable  organisms 
closely  resembles  the  cellular  structure  of  the  synthetic 
cells.  The  walls  of  such  cell-structures  are  really 
emulsoid  gels,  the  cell-fluid  being  an  emulsoid  sol. 
The  gels  which  form  the  cell-walls  and  membranes  of 
the  body  contain  albumen-  and  gelatin-like  substances 
which  swell  in  water  and  to  a  varying  degree  in  solu- 
tions of  acids,  alkalies,  and  salts.  In  other  words, 
living  protoplasm  is  essentially  a  complex  liquid  ;  the 
presence  of  a  network,  observed  in  protoplasm  which 
has  been  killed  or  "  fixed  "  by  various  reagents,  is 
not  apparently  seen  in  the  living  material.  The  so- 
called  cell-wall  of  the  protoplasm  of  some  low  forms 
of  life  appears  to  have  both  the  properties  of  a  solid 
and  of  a  liquid  substance,  and  in  this  respect  resembles 
the  film  of  a  soap  bubble.  For  example,  Chambers  has 
recently  (1917)  found  that  a  needle  can  be  repeatedly 
passed  into  living  protoplasm  without  injuring  it 


in  any  way  and  without  leaving  any  trace  of  its  track. 
Bacteria,  etc.,  penetrate  the  cell- wall  in  a  similar 
manner  without  damaging  it,  just  as  well  as  through  a 
soap-bubble.  The  outer  layer  of  protoplasm  is  not, 
however,  identical  with  the  membrane  to  which  the 
cells  owe  their  semi-permeable  properties. 

When  a  cell  dies  it  passes  from  an  emulsoid  sol  into 
an  emulsoid  gel  state  and  thereby  changes  its  character 
and  reactions,  one  of  the  most  remarkable  differences 
being  that  the  liquid  of  the  dead  cell  freely  mixes  with 
the  surrounding  watery  solution,  whilst  the  contents 
of  the  living  cell  do  not  escape  in  this  manner.  Under 
normal  conditions  living  cells  are  non-conductors  and 
are  largely  impermeable,  but  under  the  influence  of 
certain  ions  they  become  permeable  and  allow  electri- 
cally charged  particles  to  pass  freely  through  them. 
When  certain  cells  are  immersed  in  a  saline  solution 
the  sodium  ions  present  increase  their  permeability ; 
the  addition  of  calcium  ions  restores  them  to  their 
normal  condition.  Hence  simple  solutions  of  salts  do 
not  form  an  efficient  substitute  for  the  blood  or  for 
the  sea-water  in  which  marine  creatures  live  ;  a  small 
but  significant  proportion  of  calcium  salts  is  essential 
unless  a  colloid,  such  as  gelatin  or  gum-acacia,  is  added 
in  sufficient  proportion  to  give  the  saline  solution  an 
osmotic  pressure  as  high  as  that  of  the  blood.  The 
selective  permeability  of  living  cells  is  very  remarkable. 
Acids  which  are  soluble  in  the  cell  or  in  the  analogous 
liquid  bodies  readily  penetrate  the  cells,  but  other 
acids  and  strong  bases  do  not.  Weak  bases  (including 
ammonia  and  the  amines)  penetrate  the  cells  without 


Although  sodium  hydroxide  does  not  enter  the 
living  cells  it  greatly  increases  the  rate  of  oxidation 
processes  in  the  cells.  This  is  due  to  the  fact  that  the 
cell-wall  is  really  a  concentration  of  the  components 
of  the  protoplasm  of  the  cell,  and  in  the  presence  of 
sodium  hydroxide  the  normal  equilibrium  is  upset, 
and  this  produces  marked  changes  in  the  cell,  not- 
withstanding the  fact  that  the  sodium  hydroxide 
does  not  penetrate  into  it. 

The  cell  materials,  whilst  being  typical  emulsoids, 
behave  in  a  far  more  complex  manner  than  the  syn- 
thetic emulsoid  gels  or  the  natural  or  synthetic  sus- 
pension sols.  Thus,  albumen  is  electrically  neutral  and 
is  precipitated  by  basic  emulsoids  (as  histone)  and 
basic  sols,  which  are  positive  sols.  It  is  also  precipitated 
by  acid  emulsoids,  such  as  silica  sol  and  acid  dyes, 
which  are  negative  sols.  Tannin  and  gallic  acid  behave 
similarly.  Perrin  l  has  suggested  that  primary  cell 
growth  and  cell  division  are  essentially  colloidal  in 
nature,  an  idea  which  is,  to  some  extent,  supported  by 
galvanotropism  in  microscopic  animals.2  If  this  is  the 
case — and  there  is  much  evidence  in  support  of  it — a 
study  of  the  changes  in  the  viscosity  of  the  body  fluids 
under  certain  circumstances,3  the  influence  of  certain 
salts  on  the  properties  and  action  of  the  blood,4  and 
the  laws  regulating  the  permeability  of  the  cell-walls 
for  salts  and  colloids  in  the  human  body  are  bound  to 

1  Journ.  Chim.  Phys.,  1904,  II,  607. 

8  Miller,  Journ.  of  Physiol.,  1907,  215.  Buxton  and  Rahe,  Zs.  /, 
D.  Ges.,  Bischam,  XI,  n  to  12,  p.  479. 

8  Rachlmann,  Bert.  kin.  Wochensch,  1904,  Heft.  8  ;  Deutsche 
Med.  Wochensch,  1904,  Heft.  29. 

*  Nanes,  Chem.  Beih.  Physiol.,  1910,  40,  327. 


advance  our  knowledge  of  the  normal  action  of  the 
body  and  to  increase  our  power  of  treatment  when  it 
is  diseased.  As  an  instance  of  the  advance  which  has 
been  made  since  the  colloidal  nature  of  animal  and 
vegetable  substances  has  been  appreciated,  it  may  be 
noted  that  when  investigating  albumens  and  their 
digestive  products,  students  of  physiological  chemistry 
have  long  been  puzzled  by  the  complexity  of  the 
mixtures  precipitated  by  various  reagents,  such  as 
ammonium  or  zinc  sulphate.  It  has  been  impossible 
to  effect  really  satisfactory  separations  of  such  sub- 
stances by  ordinary  chemical  processes,  but  their 
strikingly  different  behaviour  towards  colloidal  metals 
has  opened  out  a  new  field  of  research  which  it  is 
anticipated  will  have  far-reaching  results.  Another 
interesting  result  of  the  recognition  of  the  colloidal 
nature  of  blood  may  suitably  be  mentioned  here. 
For  many  years  it  has  been  held  that  the  oxygen  in 
the  blood  was  in  the  form  of  a  compound  of  oxygen 
and  haemoglobin,  but  in  1907  Wolfgang  Ostwald 
pointed  out  that  all  the  available  data  may  be  arranged 
to  form  graphs  or  curves  which  are  typical  of  adsorption 
and  there  can  be  little  tfoubt  that  both  the  oxygen  and 
the  carbon  dioxide  in  the  blood  are  in  an  adsorbed 

Red  blood  -  corpuscles  are  negative,  but  can  be 
precipitated  by  both  positive  and  negative  sols. 
Henri  l  assumes  that  they  are  surrounded  by  a  pellicle 
which  can  adsorb  salts,  such  as  magnesium  and 
calcium  sulphate.  These  salts  act  on  any  precipitable 
sol,  producing  a  coagulum  around  the  corpuscles ; 

1  Compt.  Rend.,  1904,  138,  1461. 


they  can  be  removed  by  diffusion  into  an  isotonic 
sugar  solution,  after  which  blood-corpuscles  are  much 
less  susceptible  to  precipitation  by  sols. 

Blood-corpuscles  which  have  been  soaked  in  solu- 
tions of  salts — especially  chlorides  and  sulphates — are 
made  more  easily  precipitable  by  sols,  especially  ferric 
hydroxide  sol. 

The  fact  that  the  blood  is  a  typical  complex 
colloidal  fluid  is  now  accepted,  and  this  is  the  basis 
of  the  treatment  of  numerous  diseases,  though  many 
physicians  have  scarcely  recognised  it.  The  colour- 
ing matter — hczmoglobin — is  definitely  colloidal,  and 
hence  it  is  not  surprising  that  the  colouring  matter 
obtained  from  different  animals  differs  both  in  its 
composition  and  properties.  In  red  corpuscles  from 
the  human  subject,  the  haemoglobin  is  associated  with 
a  complex  of  various  substances,  some  colloidal  and 
others  crystalloidal,  and  with  a  liquid  which  is  isotonic 
with  a  solution  of  nine  parts  of  common  salt  in  a 
million  parts  of  water.  If  the  red  corpuscles  are 
immersed  in  a  more  dilute  solution  than  this  they 
swell,  and  haemoglobin  gradually  passes  from  them  to 
the  external  solution  (hczmolysis).  The  importance 
of  this  phenomena — which  is  characteristic  of  colloidal 
gels — will  be  appreciated  when  considering  the  effect 
of  colloidal  substances  in  diseased  conditions  of  the 
human  subject. 

The  characteristic  behaviour  of  some  of  the  waste 
products  of  the  human  organism  is  also  due  to  their 
colloidal  character.  Thus,  urine  contains  colloidal 
substances  which  normally  prevent  the  uric  acid  from 
separating.  This  colloid  may  be  removed  by  dialysis 


or  precipitated  by  alcohol ;  it  appears  to  be  a  deriva- 
tive of  nucleinic  acid.  Urines  which  are  deficient  in 
this  protective  colloid  may  be  prevented  from  deposit- 
ing uric  acid  on  cooling  by  adding  to  them  a  suitable 
colloid.  Unfortunately,  those  colloids,  such  as  gelatin, 
which  are  most  successful  in  vitro,  are  absorbed  by  the 
alimentary  tract  and  therefore  do  not  reach  the 
bladder  in  sufficient  quantity  to  admit  of  their  being 
used  in  certain  urinary  diseases.  Experiments  with 
other  colloids  are  now  being  made.  In  this  connection, 
it  should  be  noted  that  alcohol  reduces  the  rate  of 
diffusion  of  salts  in  gels,  whilst  urea,  chlorides,  and 
iodides  increase  it. 



THE  important  part  played  by  colloidal  sols  and  gels 
in  the  maintenance  of  hygienic  conditions  is  seldom 
realised  by  those  whose  attention  has  not  been  called 
to  this  aspect  of  the  subject.  The  removal  of  harmful 
impurities  in  water,  the  disposal  of  sewage  in  an  in- 
nocuous manner,  and  the  effective  disposal  of  "  dirt  " 
are  all  largely  dependent  on  some  colloidal  properties, 
the  precise  nature  of  which  is  by  no  means  well  recog- 
nised by  many  of  those  engaged  in  the  purification  of 
water,  or  sewage,  or  who  are  habitual  users  of  soap  and 
other  detergents. 

The  study  of  colloids  in  relation  to  these  subjects  is 
comparatively  new,  and  much  has  yet  to  be  learned. 
On  the  other  hand,  it  is  interesting  to  note  how  much 
of  the  best  modern  practice  and  use  of  colloidal  pro- 
perties has  been  reached  by  persistent  investigation 
on  the  lines  which  had  little  or  no  bearing  on  the 
recognition  of  the  real  nature  of  colloids.  Now  that 
the  importance  of  the  colloidal  state  has  been  recog- 
nised in  other  branches  of  industry  and  science,  it  is 
surely  not  too  much  to  hope  that  it  will  lead  to  equally 
striking  improvements  in  the  sphere  of  hygiene.  A 
few  words  on  each  of  the  important  subjects  of  sewage, 
water,  and  soaps  must,  however,  suffice. 

Sewage. — Sewage  consists  essentially  of  water  con- 


laminated  with  excrement,  kitchen-  and  other  domestic 
refuse,  and  matter  washed  from  roads  ;  in  some  areas 
it  may  be  further  contaminated  with  other  waste 
products  from  factories,  or  other  industries.  This 
contaminated  matter  is  in  three  forms  :  (a)  in  sus- 
pension, as  silt,  sand,  paper,  rags,  faeces,  vegetable  and 
animal  matter,  etc.  ;  (b)  colloidal  matter  in  solution 
or  pseudo-solution ;  and  (c)  in  true  solution.  In 
purifying  sewage  the  chief  purpose  is  to  separate  the 
matter  in  suspension  and  to  render  harmless  that  in 
colloidal  and  in  true  solution.  The  chief  difficulty  in 
dealing  with  sewage  is  that  the  matter  in  colloidal 
solution  prevents  the  effective  removal  of  the  coarse 
material  in  suspension,  as  well  as  assisting  in  keeping 
it  in  suspension  in  larger  proportions  than  would 
otherwise  be  the  case.  Hence,  if  the  colloidal  matter 
can  be  precipitated  in  a  suitable  form  the  most  serious 
difficulty  in  sewage  treatment  is  overcome. 

The  complex  nature  of  sewage  is  such  that  it  is 
impossible  to  treat  each  of  its  constituents  separately, 
and  this  adds  to  the  difficulty  of  purification.  It  is, 
however,  recognised  that  the  most  difficult  constituents 
are  the  colloidal  sols,  and  these  can  be  precipitated 
in  accordance  with  the  recognised  methods  for  pre- 
cipitating other  colloids.  The  most  successful  chemical 
methods  of  treatment  depend  on  a  recognition  of  this 
colloidal  character  and  on  the  coagulation  of  the 
colloidal  sol  by  the  addition  of  some  other  substance 
carrying  an  electric  charge  of  the  opposite  sign.  Ferric 
and  aluminium  hydroxides  have  been  largely  used  for 
this  purpose,  and  they  are  quite  efficient.  Their  great 
drawback  is  the  cost  of  treating  such  enormous  volumes 


of  liquid  by  any  process  of  sedimentation  and  filtration 
to  remove  the  precipitated  colloid  and  the  difficulty 
hitherto  experienced  in  converting  this  colloid  into  a 
useful  material.  The  method  which  appears  most 
likely  to  prove  of  value  consists  in  utilising  the  fact 
that  water  which  has  been  violently  agitated  with,  or 
has  fallen  through,  air  may  become  positively  charged, 
and  these  electrically  positive  particles  then  effect  the 
coagulation  of  the  negatively  charged  colloids  in  the 
sewage.  Hence,  by  agitating  the  sewage  with  air, 
under  suitable  conditions,  a  complete  coagulation  of 
its  colloidal  content  is  rapidly  effected  at  a  low  cost, 
and  the  precipitate  is  one  which  settles  with  extra- 
ordinary rapidity.  In  the  well-known  "  activated 
sludge  "  process,  air  is  blown  through  the  sewage,  the 
inventors  of  this  process  having  apparently  failed  to 
realise  that  the  electric  charge  of  the  water  particles 
is  at  least  equally  as  important  as  the  oxidising  power 
of  the  air.  A  modification  of  this  process,  in  which 
the  water  is  charged  positively  by  agitating  it  super- 
ficially with  air,  offers  still  greater  prospects  of  success, 
as  it  avoids  the  use  of  "  chemicals  "  and  the  costly 
supply  of  large  quantities  of  air.  In  this  connection  it 
is  interesting  to  note  that  beneficial  action  of  the  air 
at  the  seaside  is  probably  due  more  to  the  particles  in 
it  which  have  been  positively  charged  by  the  violent 
beating  of  the  waves  on  the -shore,  than  to  the  ozone 
to  which  this  action  is  usually  attributed.  These 
positively  charged  particles,  reacting  with  the  nega- 
tively charged  bacterial  and  other  undesirable  colloids, 
precipitate  them  and  render  them  harmless. 

The  purification  of  sewage  is  complicated  by  the  fact 


that  the  precipitation  of  the  colloidal  and  suspended 
material  is  not  sufficient  to  remove  all  the  putrefactive 
constituents  :  though  the  greater  part  is  so  removed. 
The  remainder  appears  to  be  most  advantageously 
treated  by  bacterial  action,  especially  by  the  activated 
sludge,  or  similar  process,  and,  as  it  happens,  the  two 
processes  of  precipitation  of  the  colloids  and  the 
development  of  bacterial  action  can  in  most  cases  be 
carried  on  simultaneously.  The  action  of  bacteria 
alone  (as  in  a  septic  tank)  does  not  appear  to  affect 
the  proportion  of  colloidal  matter  to  any  serious 
extent,  so  that  where  the  purification  is  confined  to 
bacterial  treatment  the  precipitation  is  more  prolonged, 
and  the  final  purification  of  the  liquid  is  much  less 
complete  than  when  the  colloids  are  precipitated  in 
the  presence  of,  or  prior  to,  the  action  of  the  putrefying 

The  sludge  produced  by  the  precipitation  of  the 
colloidal  matter  by  electrically  charged  air,  with  or 
without  the  action  of  the  activated  sludge,  is  a  fairly 
stiff  material  which  settles  rapidly  and  is  easily 
filtered,  whereas  the  ordinary  sewage  sludge  is  largely 
liquid.  The  sludge  may  suitably  be  subjected  to 
anaerobic  bacterial  action,  whereby  it  is  converted  into 
a  more  dense  and  granular  material  which  is  free  from 
the  objectionable  qualities  of  the  untreated  sludge. 

The  purification  of  water. — The  artificial  purifica- 
tion of  water  is  effected  by  colloids  : 

(1)  A  colloidal  coating  on  the  grains  of  sand  in  the 
filter   retains    (by   neutralising   the   charge)    all   the 
bacteria,  etc.,  but  not  the  colouring  matter. 

(2)  Aluminium  sulphate,  or  ferric  sulphate  (with  or 


without  alkali),  is  added  to  the  water,  and  causes  a 
precipitation  of  the  positively  charged  alumina,  or 
ferric  oxide,  which  reacts  with  the  negatively  charged 
bacteria,  clay,  etc.,  and  precipitates  them.  Simultane- 
ously, the  positively  charged  colouring  matter  is  pre- 
cipitated by  the  negatively  charged  SO4  ions,  whilst 
any  true  colouring  matter  is  adsorbed  by  the  precipi- 
tated hydroxides.  Any  excess  of  alumina,  or  ferric 
oxide,  is  precipitated  by  agitation. 

Sometimes  it  is  best  to  add  the  alkali  first ;  some- 
times only  after  the  aluminium  or  ferric  sulphate. 
The  latter  is  preferable  when  there  is  much  colouring 
matter  to  be  removed. 

The  natural  purification  of  muddy  water  is  largely 
dependent  on  its  colloidal  character.  Thus  Skey  l 
has  shown  that  suspended  mud  is  precipitated  by 
electrolytes,  including  those  in  sea  water.  Hence, 
when  a  muddy  river  flows  into  the  sea  the  proportion 
of  mud  which  settles  out,  owing  to  the  slower  current 
in  the  mixed  water,  is  insignificant  compared  with 
that  which  is  precipitated  by  the  electrolytes  in  the 
salt  water.  Schloesing  2  has  shown  that  deltas  are 
chiefly  due  to  this  cause. 

Soaps. — Sir  Edwin  Chadwick  was  a  firm  believer  in 
the  idea  that  the  effectual  preventative  of  all  forms  of 
epidemic,  endemic,  and  most  other  diseases,  is  the 
entire  removal  of  all  conditions  of  dirt,  including  foul 
air,  defective  drainage,  and  dirty  surfaces  of  all  kinds. 
He  was  most  emphatic  as  to  the  necessity  of  personal 
cleanliness,  and  on  one  occasion  he  declared  that  if  a 

1  Ghent.  News,  1868,  17,  160. 

2  Journ.  Chem.  Soc.,  1874,  30,  37. 


great  epidemic  were  to  occur  he  would  proclaim  and 
enforce  the  active  application  of  soap  and  water  as 
the  chief  preventative.  In  any  consideration  of  the 
subject  of  colloids  in  relation  to  health  and  disease, 
under  the  auspices  of  the  Chadwick  Trustees,  it  is, 
therefore,  desirable  to  point  out  that  the  detergent 
action  of  soap  to  which  Chadwick  and  his  colleagues 
attached  such  importance  is  almost  wholly  due  to  its 
colloidal  character,  by  means  of  which  it  is  able  to 
reduce  the  surface  tension  between  other  solids 
("  dirt  ")  and  water,  and  to  effect  the  removal  of  the 
former  by  a  process  of  colloidal  solution.  It  is  a 
striking  fact  that  a  i  per  cent  solution  of  soap  will 
reduce  soot  to  so  fine  a  state  of  subdivision  that  it  will 
pass  completely  through  any  filter,  and  will  remain 
suspended  indefinitely.  In  a  2  per  cent  solution  of 
soap,  on  the  contrary,  the  soot  will  be  deposited 
almost  as  rapidly  from  pure  water  !  In  a  similar 
manner  a  solution  of  soap  in  water  will  "  disperse,"  or 
bring  into  "  colloidal  solution,"  a  sufficient  proportion 
of  "  dirt  "  adherent  to  any  cleansable  surface  to  enable 
the  whole  of  the  "  dirt "  to  be  removed  in  suspension 
in  the  fluid.  The  addition  of  any  abrasive  or  scouring 
material — such  as  finely  ground  sand  or  silica  flour — 
may  aid  the  cleansing  process,  but  the  chief  feature  of 
it  is,  nevertheless,  the  production  of  a  colloidal  solution 
of  a  sufficient  proportion  of  the  "  dirt  "  to  enable  the 
remainder  to  be  removed  readily. 

The  peculiar  behaviour  of  soap  has  puzzled  many 
investigators,  some  of  whom  have  doubted  its  colloidal 
character  yet  have  failed  to  find  a  complete  explanation 
in  a  purely  chemical  conception.  The  true  nature  of 


soap  is  most  probably  shown  by  Bancroft,  who  has 
suggested  that  undissociated  soap  appears  to  be  almost 
wholly  present  in  colloidal  form,  but  in  the  presence 
of  water  the  sodium  palmitate,  or  corresponding  com- 
pound, is  hydrolised,  the  OH  ions  being  largely 
adsorbed  by  the  undissociated  soap,  the  adsorbing 
substance  then  becoming  an  anion. 



THE  microbic  origin  of  many  communicable  diseases 
is  now  generally  recognised,  and  it  is  reasonable  to 
presume  a  similar  cause  in  many  other  diseases  with 
which  no  specific  micro-organism  has  been  identified. 
Many  of  the  disease-producing  bacteria  are  sufficiently 
large  to  be  readily  visible  under  a  powerful  micro- 
scope, but  others,  such  as  those  relating  to  yellow 
fever,  foot-and-mouth  disease,  and  tobacco  disease, 
are  too  small  to  be  directly  visible.  Their  existence 
has  been  discovered  indirectly  by  means  of  the 
ultra-microscope — an  instrument  which  is  described 

Whilst  recognising  the  remarkable  advances  in  the 
treatment  of  many  diseases  which  have  resulted  from 
the  recognition  of  their  bacterial  or  protozoal  origin, 
the  fact  still  remains  that  by  far  the  most  marvellous 
preventatives  of  disease  are  contained  within  a  normal, 
healthy  body,  in  which,  as  Lister  has  clearly  demon- 
strated, bacteria  can  only  establish  themselves  when 
conditions  have  arisen  which  create  a  state  of  un- 

The  period  in  which  all  zymotic  diseases  were 
attributed  solely  to  the  introduction  of  bacteria,  or 
protozoa,  into  the  otherwise  healthy  subject  is, 
happily,  passing  away,  and  pathologists  and  others 



are  increasingly  recognising  as  a  fact  the  necessity  for 
the  bodily  conditions  being  suitable  before  the  disease 
germs  can  multiply  extensively  in  it.  As  a  result  of 
the  wide  recognition  of  this  fact — originally  pointed 
out,  though  expressed  in  different  terms,  by  Sir  Edwin 
Chadwick  and  his  colleagues — it  is  now  seen  that 
attention  should  be  concentrated  on  the  state  of  the 
body  fluids  and  cells  as  well  as  on  the  invading  micro- 
organisms. Now  that  the  colloidal  nature  of  the  body 
fluids  and  cells  has  been  recognised,  it  is  possible  to 
make  considerable  progress  in  maintaining  them  in, 
or  restoring  them  to,  a  suitable  condition  on  purely 
chemical  or  physio-chemical  lines.  The  subject  is  too 
vast  to  discuss  in  detail  in  the  present  volume,  but 
briefly  it  is  now  admitted  that  if  the  normal  colloidal 
condition  of  any  of  the  more  important  body  fluids,  or 
cells,  is  disturbed  by  the  advent  of  undesirable  electro- 
lytes, salts,  or  colloids  of  the  "  opposite  "  sign,  condi- 
tions are  produced  which  provide  a  suitable  nutrient 
medium  for  many  of  the  disease-producing  germs  which 
are  constantly  coming  into  contact  with  the  body.  If 
the  altered  body  fluids  or  cells  can  be  restored  to  their 
normal  colloidal  state  without  seriously  damaging 
any  other  portion  of  the  subject,  the  invading  germs 
will  soon  perish  and  will  be  removed  from  the  body 
by  the  normal  processes  of  life.  If  this  view  of  the 
matter  is  correct,  it  is  of  far  greater  importance  to 
restore  the  disarranged  colloidal  state  to  its  normal 
condition  than  it  is  to  endeavour  to  kill  the  invading 
germs  without  otherwise  altering  the  state  of  the 
diseased  or  altered  cells  or  body  fluids.  In  the  latter 
event  it  will  only  be  a  question  of  time  before  the 


patient  is  attacked  by  further  organisms,  and  these 
attacks  will  be  continued  until,  by  some  means  or  other, 
the  diseased  organs  regain  their  normal  colloidal  state, 
or  until  they  are  atrophied  or  have  been  removed  by 
means  of  a  surgical  operation.  If,  on  the  contrary, 
the  normal  colloidal  state  of  the  diseased  organ  can 
be  restored,  the  body  as  a  whole  is  well  able  to  effect 
a  complete  recovery  without  any  serious  risk  or  delay. 
The  importance  of  the  influence  of  the  "  soil "  upon 
the  "  seed,"  and  the  predisposition  of  the  individual 
body  to  attacks  by  germs,  has  been  established  by 
Sir  Wm.  Collins  in  an  essay  published  in  1884, 
dedicated  to  Herbert  Spencer,  who  "  regarded  it  as 
opening  the  way  to  a  considerable  reform  in  pathology." 
If  his  theory  (as  to  underestimated  influence  of  evolu- 
tion on  the  specific  disease-producing  effects  of  or- 
ganisms whose  cycle  may  be  only  a  few  hours  or  even 
less  than  one  hour,  and  whose  rate  of  propagation  is 
incalculable)  is  approximately  correct  the  necessity  of 
maintaining  the  body  fluids  in  the  correct  colloidal 
state  must  be  obvious.  The  rational  treatment  of 
zymotic  disease  must  not  depend  solely  on  the  destruc- 
tion of  the  germs  by  means  of  which  the  disease  is 
propagated ;  the  requisite  attention  must  also  be 
paid  to  the  "  soil,"  or  medium,  in  which  the  germs 
exist  in  the  body. 

This  is  readily  understood  when  it  is  realised  that 
emulsions  of  bacteria  may  be  regarded  as  suspensoids 
protected  by  an  emulsoid  sol.  They  are  precipitated 
by  definite  amounts  of  electrolytes,  such  as  acids, 
heavy  metal  ions,  and  by  aluminium  and  ferric  ions, 
as  are  ordinary  suspensions.  Emulsions  of  bacteria 


are  not  precipitated  by  alkalies  and  are  not  protected 
from  precipitation  by  other  emulsoids,  such  as  gelatin, 
as  are  many  negative  colloids.  The  addition  of  an 
immune  serum  to  a  bacteria  sol  greatly  increases 
the  sensitiveness  of  the  latter  to  electrolytes,  and 
apparently  destroys  the  protecting  part  of  the  bacteria 
sol,  which  thus  becomes  a  suspensoid  sol. 

Unfortunately,  the  colloidal  characteristics  of  fluids 
containing  bacteria  are  highly  complex.  Many  of  their 
reactions  appear  to  be  partly  of  a  colloidal  and  partly 
of  a  chemical  nature.  Thus,  the  reaction  between 
bacteria  and  agglutinins,  including  emulsin  and  gelatin, 
resembles  an  adsorption,  but  as  sols  of  any  one  kind  of 
bacteria  are  affected  only  by  the  agglutinin  produced  in 
the  serum  by  the  injection  into  the  animal  of  the  same 
kind  of  bacteria,  this  fact  seems  to  imply  the  existence 
of  definite  chemical  properties.  On  the  other  hand 
some  bacteria  sols  are  definitely  affected  by  inorganic 
colloids  in  a  manner  which  suggests  both  a  colloidal  and 
a  chemical  action. 

Toxins  and  anti-toxins. — Toxins  are  the  products  of 
bacterial  life,  and  are  to  some  extent  analogous  to  the 
excreta  of  the  higher  organisms.  They  are  decom- 
posed and  rendered  harmless  by  a  number  of  sub- 
stances, of  which  special  interest  attaches  to  those 
other  products  of  bacterial  life  (such  as  immune  serum) 
known  as  anti-toxins.  Thus,  when  a  suitable  immune 
serum  is  added  to  the  corresponding  bacteria  sol, 
the  latter  does  not  coagulate,  even  after  dialysis,  but 
it  becomes  so  sensitive  to  electrolytes  that  the  latter 
coagulate  it  easily.  This  is  explained  by  the  suggestion 
that  the  agglutinin  in  the  serum  destroys  a  protecting 


agent  which  is  assumed  to  be  present  in  the  bacteria 

A  mixture  of  the  corresponding  agglutinin  and 
bacteria  sol  is  not  precipitated  by  OH  ions,  but 
readily  so  by  acids  and  salts  of  the  heavy  metals. 
The  addition  of  salts  precipitates  the  colloids  if  there 
is  an  equivalent  of  agglutinin  to  bacteria  sol.  If  either 
colloid  is  greatly  in  excess  of  the  other  no  precipitation 

Both  toxins  and  anti-toxins  are  colloidal,  particu- 
larly the  latter.  Thus,  when  a  diphtheria  toxin  is  treated 
with  its  anti-toxin,  the  reduction  in  toxicity  depends  on 
the  manner  of  administration.  If  the  anti-toxin  is 
added  in  small  quantities  at  long  intervals  much  more 
anti-toxin  is  needed. 

Field  and  Teague  1  found  that  both  toxin  and  anti- 
toxin migrate  distinctly  in  an  electric  field.  There 
may  be  a  chemical  compound  between  the  toxin  and 
the  anti-toxin,  but  more  probably  there  is  a  mutual 
adsorption,  the  reaction  being  wholly  colloidal.  A 
difficulty  exists  with  both  explanations,  inasmuch  as 
diphtheric  anti-toxin  is  the  only  one  which  will  neu- 
tralise the  diphtheria  toxin,  and,  at  present,  both 
these  substances  appear  to  possess  both  chemical  and 
colloidal  properties. 

In  addition  to  the  difficulty  of  treating  such  com- 
plex substances  in  accordance  with  general  principles, 
there  is  the  further  disadvantage  that,  whilst  blood 
serum  has  normally  a  positive  charge,  most  of  the  sols 
of  the  pathogenic  bacteria  are  not  coagulated  by  fluids 
with  such  a  charge.  This  remarkable  behaviour  may 

1  Journ.  Exp.  Med.,  IX,  86. 


be  due  in  part  to  the  presence  of  a  powerful  protecting 
agent,  but  if  this  is  correct  it  only  transfers  the  diffi- 
culty without  eliminating  it.  The  value  of  a  suitable 
immune  serum  lies  in  its  power  of  increasing  the 
sensitiveness  of  the  bacteria  sols  to  electrolytes,  and 
thus  facilitating  their  precipitation.  Much  work  is 
now  being  done  in  the  endeavour  to  ascertain  the 
chemical  or  colloidal  nature  of  the  various  agglutinins, 
and  until  the  results  of  this  work  have  been  published 
judgment  on  this  matter  must  be  deferred.  The  fact 
that  so  small  a  quantity  of  the  agglutinins  has  such 
far-reaching  effects  is  highly  confirmatory  of  their 
essentially  colloidal  character,  and  their  peculiar 
specificity  may  ultimately  be  found  to  be  due  to  the 
simultaneous  production  by  the  bacteria  of  a  specific 
protecting  agent  which,  in  its  turn,  may  be  decomposed 
by  the  elementary  colloidal  sols,  though  it  resists  the 
attack  of  compound  sols.1 

1  Further  information  on  the  current  views  of  the  reactions 
between  agglutinins  and  bacteria  will  be  found  in  : 

Immuno-chemistry,  S.  Arrhenius  (Macmillan  and  Co.). 

Le  mechanisms  de  V agglutination,  J.  Bordet.  Annales  de  VInst, 
Pasteur,  13,  pp.  225  to  272. 

"  Mechanism  of  the  Agglutination  of  Bacteria  by  Specific  Sera," 
W.  J.  Tulloch,  Biochem.  Journ.,  8,  pp.  294-319. 



THE  similarity  between  the  poisoning  of  animals  and 
the  stoppage  of  the  reaction  of  certain  metallic  sols  by 
small  quantities  of  well-known  poisons  is  very  striking. 
Thus,  the  presence  of  a  trace  of  prussic  acid  will  reduce 
the  speed  of  reaction  of  platinum  sol  on  hydrogen  per- 
oxide to  half  the  normal  rate,  and  a  somewhat  larger 
proportion  will  cause  the  reaction  to  cease.  Enzymes 
and  ferments  are  "  poisoned  "  in  a  similar  manner. 

This  great  similarity  between  animal  "poisoning" 
and  a  stoppage  of  a  relatively  simple  chemical  reaction 
is  very  important,  as  it  suggests  many  other  points  of 
possible  resemblance  which  are  worth  further  study 
and  opens  out  large  fields  of  chemical  research  in 
connection  with  biological  and  physiological  problems. 
Moreover,  the  relative  ease  with  which  the  effect  of 
metal  and  other  sols  on  chemical  reactions  can  be 
studied  and  controlled,  suggests  that  similar  reactions 
— equally  well  controlled — may  be  effected  in  the 
human  subject  with  far-reaching  results. 

Digestion  and  colloids. — The  reactions  which  occur 
in  normal  digestion  result  in  the  production  of  sub- 
stances which  are  able  to  pass  through  the  membrane 
of  the  alimentary  canal  into  the  blood  stream.  At  the 
first  glance,  it  may  be  supposed  that  such  a  passage 
would  exclude  all  colloidal  sols,  though  precisely  the 



opposite  is  the  case.  It  has  been  found  that  in  the 
presence  of  a  crystalloid,  such  as  common  salt,  the 
passage  of  colloidal  sols  through  the  membranes  is 
considerably  increased,  thus  showing  the  importance 
of  the  salt  to  the  animal  and  human  organism.  The 
advisability  of  eating  salt  with  so  typical  a  colloidal 
gel  as  a  boiled  egg  is  thus  seen  to  be  based  on  a  physi- 
ological requirement,  and  not  merely  on  a  matter  of 

It  is  important  to  observe  that  the  products  of 
digestion,  and  some  other  colloidal  substances  occur- 
ring in  the  animal  organism,  consist  of  much  smaller 
particles  than  artificially  prepared  colloids.  Thus 
haemoglobin  will  pass  through  much  less  permeable 
membranes  than  colloidal  metals,  and  serum,  albumen, 
and  -  protalbumoses  are  correspondingly  finer  in  the 
order  given.  This  may  partially  account  for  their 
ability  to  pass  through  certain  membranes.  Donnan 
has  shown  that  the  permeability  of  a  membrane  to  a 
simple  ion  is  greatly  affected  by  the  presence  of  a  colloid. 
In  some  cases  the  colloid  is  hydrolised  by  some  un- 
known means  in  the  presence  of  an  inert  membrane 
and  an  electric  potential  is  created.  In  both  these 
cases  the  difference  between  a  living  and  a  dead 
organism  must  not  be  overlooked,  though  its  import- 
ance should  not  be  exaggerated. 

The  nature  of  materials  used  for  food  is  so  varied 
and  the  products  of  their  digestion  are  so  numerous 
that  for  anyone  who  realises  their  essentially  colloidal 
nature,  it  is  easy  to  see  that  any  change  of  state  may 
produce  a  profound  disturbance  in  the  whole  system, 
and  that  such  a  disturbance  may  appear  to  be  quite 


out  of  proportion  to  the  chemical  activity  of  any 
compound  or  element  which  may  be  present.  For  this 
reason  there  can  be  no  general  cure  for  all  forms  of 
indigestion,  as  each  has  its  specific  cause.  If  any  such 
general  remedy  could  exist  it  would  be  a  substance 
which  would  effect  the  conversion  of  any  food  sub- 
stance into  a  colloidal  sol  of  a  nutritive  and  non-toxic 

Similarly,  it  is  possible  to  see  that  improper  food, 
unsuitably  prepared,  the  absence  of  sufficient  air,  and 
the  neglect  of  sanitary  and  hygienic  precautions  may 
effect  changes  which  are  quite  disproportionate  to  the 
actual  weight  of  "  dirt  "  or  other  objectionable  matter 
present.  The  normal  state  of  the  body  fluids  is  easily 
disturbed,  and  whilst  it  is  almost  as  easily  restored 
under  healthy  conditions  of  life,  restoration  is  made 
difficult  or  even  impossible  if  the  conditions  are  un- 



COLLOIDS  have  long  been  used  more  or  less  unwittingly 
in  medicine,  the  colloidal  state  being  the  only  one  in 
which  certain  medicaments  can  be  administered,  whilst 
others — exhibited  as  tinctures — are  converted  into 
colloids  on  dilution.  Such  crude  forms  are  necessarily 
subject  to  many  disadvantages,  and  the  true  signifi- 
cance of  their  colloidal  nature  not  having  been  recog- 
nised it  is  only  natural  that  they  should  not  be  either 
as  certain  in  action  nor  as  free  from  objectionable 
properties  as  colloids  which  have  been  specially  pre- 
pared so  as  to  secure  the  maximum  colloidal  efficiency. 
Thus,  tincture  of  podophyllin  and  other  resinous  sub- 
stances are  precipitated  on  diluting  them  sufficiently 
with  water,  with  the  consequent  formation  of  a  small 
proportion  of  colloidal  sol.  This  sol  is  the  most  active 
therapeutic  constituent,  and  the  remaining  material 
is  only  useful  medicinally  when  it  has  been  converted 
by  the  action  of  the  body  fluids  into  an  assimilable 
form.  This  conversion  is  accompanied  by  a  serious 
loss  of  material,  both  directly,  by  its  conversion  into 
inert  or  undesirable  substances,  and  indirectly  by  its 
transport  to  portions  of  the  organism  where  it  cannot 
exercise  the  desired  effect.  Consequently,  the  acci- 
dental production  of  therapeutic  agents  in  colloidal 



form  results  in  uncertainty  of  action,  the  production 
of  undesirable  side  reactions,  and  necessitates  the 
administration  of  large  doses,  the  greater  part  of  which 
is  inert,  or,  in  some  cases,  somewhat  harmful  to  the 
patient.  These  disadvantages  were  unavoidable  so 
long  as  no  satisfactory  colloidal  preparations  were 
available,  but  with  the  increase  in  the  number  and 
efficiency  of  the  latter,  the  science  of  pharmacology 
and  the  practice  of  medicine  will,  it  is  anticipated, 
make  rapid  progress. 

The  most  widely-used  preparations  of  a  highly 
colloidal  character  are  the  embrocations  and  liniments 
used  externally  or  those  administered  internally  in  the 
form  of  emulsions  of  cod  liver  oil,  petroleum,  etc. 
These  have  proved  a  convenient  and  satisfactory  means 
of  introducing  certain  liquids  in  varying  degrees  of 
dilution,  under  conditions  in  which  ordinary  solvents 
are  inadmissible. 

Such  emulsions  are  truly  colloidal  in  character,  the 
active  liquid  being  usually  present  as  the  disperse 
phase,  whilst  the  continuous  phase  is  of  a  different 
character,  such  as  water  to  which  a  small  proportion 
of  an  emulsifying  agent — usually  albumen  or  a  soap — 
is  added.  Other  active  therapeutic  agents  may  usually 
be  present  in  solution  in  the  aqueous  phase,  it  being 
an  additional  advantage  possessed  by  emulsions  that 
they  permit  the  simultaneous  exhibition  of  two  or  more 
active  agents  in  any  desired  degree  of  concentration. 

Emulsions  of  the  kind  just  mentioned  must  not  be 
confused  with  the  colloidal  sols  described  later.  Even 
the  most  elegant  emulsions  are  very  coarse  compared 
with  the  sols,  and  the  penetrating  power  and  general 


activity  of  the  latter  are  correspondingly  greater  than 
that  of  emulsions. 

The  customary  administration  of  any  remedy — 
quite  apart  from  the  particular  substance  or  drug 
which  it  may  contain — is  primarily  based  on  the 
assumption  that  such  a  remedy  has  a  specific  reaction 
either  with  a  substance  in  the  body  (such  as  the  action 
of  pepsine  on  the  undigested  food)  or  an  equally  definite, 
but  less  understood,  reaction  whereby  certain  organs 
are  stimulated  to  unusual  effort,  as  in  the  administra- 
tion of  emetics  or  purgatives.  It  is  generally  supposed 
that  the  effect  is  roughly  proportional  to  the  dose 
administered,  though  it  is  recognised  that  the  optimum 
dose  differs  with  different  patients.  In  some  cases— 
particularly  in  the  administration  of  mercury  com- 
pounds— it  is  also  realised  that  minute  quantities 
administered  frequently  have  an  effect  which  is 
entirely  different  from  that  of  the  same  substance 
administered  in  a  single  and  large  dose.  Still  more 
striking  is  the  fact  previously  mentioned,  that  with 
some  remedies  the  changes  are  out  of  all  proportion 
to  the  dose  which  may  be  administered.  The  great 
changes  which  occur  in  certain  diseases  are  prevented, 
and  the  normal  state  is  restored  by  quantities  of 
chemical  agents  which  appear  ridiculously  small  when 
regarded  as  definite  reagents.  But  such  a  condition 
is  a  well-known  characteristic  of  colloidal  fluids,  in 
which  even  a  few  drops  of  solution  will  effect  a  solidifica- 
tion of  a  large  volume  of  material.  The  coagulation  of 
milk  by  rennet  or  acid,  and  that  of  blood  after  a  short 
exposure  to  air,  are  typical  illustrations  of  such  a 
change.  The  extraordinarily  rapid  action  of  minute 


doses  of  some  poisons  is  probably  a  similar  effect. 
Bearing  in  mind  these  great  changes  in  condition 
which  result  from  the  action  of  small  amounts  of  active 
agents,  it  is  easy  to  see  that  a  slight  excess  or  deficiency 
of  some  element  present  in  minute  proportions  in  the 
organism  may  effect  a  profound  change  in  the  action 
of  that  organism.  The  deficiency  of  phosphorus  in 
certain  nervous  diseases  is  well  recognised,  and  various 
methods  of  supplying  it  have  met  with  encouraging 
results.  There  is,  however,  a  curious  idea  extant,  that 
an  element  in  which  there  is  a  deficiency  should  be 
administered  in  the  same  form  as  that  in  which  it 
exists  in  the  body.  For  instance,  there  is  a  popular 
idea  that  glycophosphates  are  superior  to  any  other 
phosphorus  compounds,  because  the  phosphorus  in 
the  brain  is  chiefly  found  as  a  glycophosphate.  This 
is  quite  a  mistake,  as  will  readily  be  seen  if  other 
analogous  cases  are  considered.  For  instance,  sugar 
is  stored  in  the  liver  in  the  form  of  glycogen,  but  to 
administer  glycogen  orally  would  be  useless,  as  it  is 
destroyed  in  the  stomach.  It  is  essential  that  any 
medicine  should  be  administered  in  such  a  form  that 
its  essential  constituent  will  travel  through  the  body 
until  it  reaches  the  part  where  it  is  required,  and  that 
it  shall  arrive  at  that  organ  in  such  a  state  as  to  be 
used  to  the  greatest  advantage.  To  administer  lecithin 
because  lecithin  has  been  isolated  from  the  brain 
substance  is  to  misunderstand  the  chemical  changes 
which  take  place  in  assimilation,  and  to  supply  the 
subject  with  a  material  in  a  form  from  which  it  has  to 
be  converted  to  something  more  suitable.  The  fact 
that  this  conversion  occurs  merely  shows  how  marvel- 


lous  an  alchemist  is  the  human  organism  ;  it  is  no 
reason  for  the  administration  of  chemical  agents  in 
unsuitable  forms. 

The  principle  underlying  the  treatment  of  disease 
by  the  administration  of  chemical  compounds  is  much 
more  easily  understood  when  it  is  realised  that  the 
reactions  deal  largely  with  colloidal  materials,  and 
that  they  may  be  effected  most  efficiently  and  with  a 
minimum  of  disturbance  to  other  organs  by  basing 
the  treatment  on  this  principle. 

This  fact  has  been  recognised  in  a  half-hearted  way 
for  some  years,  but  its  implications  were  scarcely 
realised  until  a  few  years  ago.  This  was  due  to  a 
number  of  causes,  of  which  the  two  most  important 
were  the  difficulty  of  studying  the  special  properties  of 
substances  in  the  colloidal  state  with  the  appliances 
then  at  hand,  and  the  difficulty  experienced  in  obtain- 
ing active  colloidal  fluids  which  were  isotonic  with 
and  therefore  stable  in  the  body  fluids  to  which  they 
were  applied.  The  work  of  Ehrlich  and  others  may, 
in  certain  respects,  be  regarded  as  attempting  to 
supply  elements  of  a  highly  toxic  character,  such  as 
arsenic,  in  such  a  form  that  they  would  affect  the 
disease-creating  germs  without  harming  the  patient 
or  host.  Such  methods  suffer  from  obvious  draw- 
backs, such  as  the  caustic,  irritant,  or  even  toxic  effect 
of  the  stabilising  organic  compound,  and  as  the  com- 
plexity of  the  compounds  was  increased,  their  essentially 
colloidal  character  gradually  receded  into  the  back- 
ground of  the  minds  of  the  investigators  until  it  was 
wholly  overlooked. 

Colloidal    fluids    only    retain    their    characteristic 


properties  so  long  as  their  active  ingredient  is  in  a 
properly  dispersed  and  suitable  colloidal  state.  In  the 
presence  of  very  small  quantities  of  certain  salts,  the 
ions  or  ultimate  particles  of  which  have  an  electric 
charge  which  is  opposite  in  sign  to  that  of  the  active 
colloid,  the  latter  will  be  coagulated  and  rendered  in- 
active, unless  they  have  been  protected  by  some  other 
colloid.  In  the  latter  case,  coagulation  or  precipitation 
can  only  occur  when  the  protective  agent  has  been 
destroyed  or  removed. 

Medical  possibilities  of  colloids. — From  what  has 
already  been  stated  it  will  be  seen  that  the  application 
of  colloidal  sols  to  diseased  conditions  of  the  human 
body  is  distinctly  encouraging,  but  like  all  other  new 
ideas  it  has  had  its  share  of  drawbacks  and  discourage- 
ments, due  in  almost  every  instance  to  ignorance. 
Among  other  causes  the  premature  supply  of  improperly 
prepared  and  unstable  colloids  has  been  one  of  the 
most  serious  sources  of  trouble. 

Shortly  after  the  definite  recognition  of  the  colloidal 
nature  of  the  chief  body  fluids  was  effected,  the 
enormous  possibilities  which  might  result  from  the 
application  of  colloidal  disinfectants  and  medicines 
were  rapidly  recognised  by  German  investigators  ;  a 
number  of  colloidal  substances  was  placed  on  the 
market  and  their  therapeutic  properties  were  carefully 
and  vigorously  "  boomed "  in  this  country  and 

It  was  soon  found,  however,  that  most  of  these 
preparations  rapidly  deteriorated  in  value  ;  some  of 
them  were  so  unstable  that  they  contained  no  active 
colloid  at  the  time  when  they  were  used,  and  others — 


not  being  isotonic  with  the  physiological  fluids  in  the 
diseased  organs  to  which  they  were  applied — were 
coagulated  immediately  after  their  administration  to 
the  patient. 

Many  attempts  to  secure  stability  by  means  of 
organic  compounds  were  made,  and  eventually  the 
main  difficulties  were  overcome — especially  with  regard 
to  certain  colloidal  elements.  One  of  the  chief  causes 
of  trouble  was  due  to  the  fact  that  if  a  colloidal  sub- 
stance is  prepared  in  the  purest  possible  state  in  a 
disperse  medium  (such  as  water)  of  great  purity,  the 
product  will  be  highly  unstable.  Even  a  trace  of 
material  of  the  opposite  electric  sign  will  cause  the 
precipitation  of  the  colloid.  If,  on  the  contrary,  the 
substance  is  converted  into  the  colloidal  state  in  the 
presence  of  certain  other  colloids  and  of  certain  salts, 
the  desired  colloid  will  not  have  its  activity  impaired 
in  the  least  degree,  but  it  will  be  quite  stable  and  can  be 
mixed  with  normal  blood  or  other  body  fluids  without 
being  rendered  inactive  by  them.  The  salts  and 
additional  colloids  exercise  a  protective  action  on  the 
colloid  chiefly  under  consideration,  and  so  enable  it  to 
be  used  under  circumstances  which  would  otherwise 
be  impossible.  The  therapeutic  action  of  the  protec- 
tive agent  must  not  be  overlooked  ;  usually  it  appears 
to  be  negligible,  but  occasionally  it  has  been  observed 
to  be  of  considerable  importance. 

Failure  to  realise  the  necessity  for  stabilising  the 
remedial  colloids  by  rendering  them  isotonic  with  the 
blood  serum,  and  protecting  them  against  precipitation 
by  undesirable  agents,  was  thus  one  of  the  chief  causes 
of  failure  of  the  earlier  investigators,  but  it  has  been 


entirely  overcome  in  the  case  of  a  large  number  of 
colloidal  sols  mentioned  later,  and  these  are  quite 
stable  and  effective.  Yet  in  consequence  of  the  failure 
which  resulted  from  such  ignorance  of  the  essential 
properties  of  all  colloidal  fluids,  British  medical  men 
were  at  first  rightly  averse  to  using  colloidal  pre- 
parations, and  the  subject  remained  in  a  parlous 
state  for  some  time.  In  fact,  it  so  remained  until 
suitable  methods  of  preparing  stable  and  isotonic 
colloidal  sols  were  discovered  in  1910-1913  by  the 
late  Henry  Crookes — a  son  of  Sir  Wm.  Crookes — and 
were  extended  and  improved  by  his  colleagues  and 
successors,  as  well  as  by  other  investigators. 



ANY  substance  can  be  obtained  in  the  colloidal  state 
if  the  conditions  under  which  it  is  prepared  are  suit- 
able. All  colloidal  sols  are  prepared  by  either 

(1)  Dispersing  or  breaking  down  the  larger  particles 
in  the  presence  of  a  suitable  fluid  ;   or 

(2)  By   "  condensing "   particles   in  solution  until 
they  form  larger  suspensoid  particles. 

The  dispersion  may  be  effected — 

(a)  Mechanically,  as  by  grinding  the  substance 
and  fluid  together  ; l 

(b)  By  dilution,  as  when  a  gum  is  dissolved  in 
alcohol  solution  and  the  solution  poured  into  a  large 
volume  of  water  ; 

(c)  By  using  electrodes  of  the  substance  to  be  dis- 
persed immersed  in  a  suitable  liquid  and  passing  an 
electric  current  through  them  ; 

(d)  By  the  addition  of  a  suitable  electrolyte  (such 

1  Colloidal  solutions  must  not  be  confounded  with  the  sugges- 
tions made  by  homcepathists  with  respect  to  prolonged  trituration 
of  a  solid  material  or  to  the  administration  of  small  doses  at  regular 

No  trituration,  however  prolonged,  will  convert  some  materials 
into  a  colloidal  sol  state,  and  even  those  which  can  be  converted 
are  too  much  contaminated  with  non-colloidal  material  and  are 
too  unstable  to  be  of  much  service.  As  regards  dosage,  it  is  a 
well-known  characteristic  of  all  colloidal  reactions  that  if  the  whole 
of  the  reagent  is  added  rapidly  its  effect  is  much  greater  than  if  it 
is  added  in  small  quantities  at  a  time. 



as  an  acid  or  alkali)  to  a  colloidal  gel.  From  the 
analogy  between  this  process  and  that  of  animal 
digestion  it  is  frequently  termed  peptisation. 

The  condensation  may  be  effected  by  chemical 
reduction,  oxidation,  hydrolysis,  or  double  decom- 
position. Thus,  colloidal  gold  sol  is  readily  obtained 
by  reducing  a  dilute  solution  of  gold  chloride,  formic 
aldehyde,  or  phosphorus  in  the  presence  of  potassium 
carbonate.  Colloidal  sulphur  sol  may  be  obtained  by 
adding  a  solution  of  sodium  hyposulphite  drop  by 
drop  to  a  dilute  solution  of  sulphuric  acid,  heating 
the  mixture  to  80°  C.  for  a  short  time,  filtering  off 
any  insoluble  sulphur  and  neutralising  with  sodium 

Although  many  colloidal  sols  are  made  by  hydrolysis 
(i.e.  by  the  action  of  water  on  them)  this  is  seldom 
used  as  a  method  of  preparation.  The  methods  of 
preparation  just  indicated  do  not  as  a  rule  yield 
colloids  which  are  stable  in  the  presence  of  serum. 
For  this  purpose  they  must  be  modified  so  as  to  pro- 
duce a  stable  fluid.  It  is  most  important  to  observe 
that  it  is  relatively  easy  to  produce  a  colloidal  sol  of 
low  stability  and  containing  a  considerable  proportion 
of  impurities  ;  it  is  peculiarly  difficult  to  prepare  pure 
sols  which  remain  stable  when  mixed  with  the  blood- 
serum  and  other  physiological  fluids.  Yet  the  use  of 
impure  and  unstable  sols  is  so  serious  that  no  pains 
must  be  spared  in  ensuring  the  purity  and  stability 
of  the  sols  used  for  remedial  purposes,  and  particu- 
larly those  which  are  administered  by  intravenous 
or  intramuscular  injection.  For  these  reasons,  the 
remedial  colloidal  sols  prepared  by  the  amateur  should 


not  be  used  until  exhaustive  tests  have  proved  their 
efficacy  and  stability.  The  author  is  aware  of  a  number 
of  severe  cases  of  poisoning  which  were  due  solely  to 
the  use  of  impure  colloids  with  a  very  low  degree  of 
stability.  As  many  colloidal  sols  of  high  stability  and 
suitability  for  administration  either  orally  or  hypo- 
dermically  can  now  be  purchased,  there  is  little  or  no 
advantage  to  be  gained  by  medical  men  preparing 
these  sols. 

The  stabilising  or  protecting  of  a  colloidal  sol  depends 
on  its  being  in  a  state  of  equilibrium  between  the 
forces  tending  to  cause  these  small  particles  to 
coalesce  (surface  tension)  and  those  tending  to  cause 
dispersion  of  the  colloid  throughout  the  medium. 
Stability  appears  to  be  due,  in  most  cases,  to  a  union 
of  the  particles  to  be  stabilised  with  those  of  the  pro- 
tective colloid  or  with  ions  which  have  a  stabilising 
action.  Zsigmondy  maintains  that  stability  is  wholly 
due  to  the  equilibrium  between  the  adsorption  and 
dissociation  of  ions  by  colloidal  particles.  The  in- 
stability which  is  most  serious  in  colloidal  sols  used  as 
medicines  is  that  which  results  in  coagulation. 

Stability  is  secured  in  a  variety  of  ways,  including 
the  following  : 

(a)  Preparing  the  sol  in  the  presence  of  those  sub- 
stances in  which  it  is  required  to  be  stable,  i.e.  by 
substituting  an  appropriate  fluid  for  water  as  a  solvent 
for  the  various  substances  from  which  the  colloid  is 
produced.  Thus  colloidal  sulphur,  prepared  in  a 
solution  in  which  water  is  replaced  by  a  physiological 
salt  solution,  is  much  more  stable  after  injection  into 
the  blood  than  colloidal  sulphur  prepared  in  pure 


water.  On  the  other  hand,  the  former  is  liable  to  set 
up  undesirable  reactions  within  the  body  unless 
special  precautions  are  taken  to  remove  the  undesir- 
able salts  by  a  process  of  selective  dialysis. 

(b)  Adding  a  protective  agent  such  as  gelatin  or  pro- 
talbinic  acid  prior  to  producing  the  sol. 

(c)  Preparing  the  sol  so  that  all  the  dispersed  par- 
ticles are  of  the  same  size  and  without  any  appreciable 
surface  tension  in  the  dispersing  fluid. 

(d)  The  presence  of  chlorine  or  of  other  charac- 
teristic ions  appears  to  be  essential  to  the  stability 
of  positive  sols.    If  these  ions  are  removed  the  sols  are 

(e)  Removing  the  greater  part  (but  not  the  last  traces) 
of  electrolytes.    This  method  is  inapplicable  to  colloids 
used  for  medical  purposes. 

Assaying  sols. — It  is  of  utmost  importance  to  de- 
termine the  activity  of  a  sol  just  prior  to  its  use  unless 
it  is  definitely  known  that  it  is  sufficiently  stable  for 
its  activity  to  be  relied  on  implicitly. 

The  percentage  of  active  colloid  cannot  be  de- 
termined by  any  of  the  ordinary  chemical  methods  as 
the  colloidal  state  is  physical  rather  than  chemical  in 
character.  Thus,  a  colloidal  solution  of  silver  gives  no 
precipitate  with  a  solution  of  a  chloride,  a  colloidal 
solution  of  iodine  does  not  produce  a  blue  colour  with 
starch  solution.  Hence,  it  sometimes  happens  that  a 
chemist  may  report  that  a  certain  solution  does  not 
contain  a  particular  element  or  compound  if  the  latter 
is  in  a  colloidal  sol  state.  By  appropriate  treatment — 
usually  by  converting  the  substance  into  the  crystalloid 
state — the  ordinary  methods  may  be  applied,  but  they 


do  not  differentiate  between  the  proportions  of  colloidal 
and  crystalloidal  substance  when  both  are  present. 

The  chief  methods  of  determining  the  activity  and 
therefore  the  value  of  the  sol  are  : 

(a)  Observation  of  the  movement  of  the  particles 
by  means  of  an  ultra-microscope. 

(b)  Observation  of  the  intensity  of  the  Tyndall 

(c)  Determination  of  the  gold  number. 

(d)  Observation  of  the  time  taken  for  a  deposit 
to  form. 

(e)  Observation  of  the  effect  of  the  addition  of 
the  solution  to  serum  or  other  characteristic  physio- 
logical fluid. 

A.  Arc  Lamp.         B.  Slit.         C.  Primary  Lens.         D.  Secondary 'Lens. 
E.  Condenser  (  I  in.  objective).  F.  Cuvette.  G.  Microscope. 


(a)  The  ultra-microsoope  affords  the  simplest  and 
most  rapid  means  of  ascertaining  the  activity  of  the 
colloidal  particles  in  a  sol.  When  properly  prepared, 
colloidal  sols  are  transparent  or  slightly  opalescent, 
coloured  or  colourless,  pass  readily  through  a  filter 
paper,  are  apparently  homogeneous  in  chemical  be- 
haviour but  under  the  ultra-microscope  are  seen  to 
contain  minute  particles  in  a  state  of  rapid  motion,  the 
particles  being  comparable  in  size  to  those  of  molecules 


in  crystalloid  solutions.  In  some  colloidal  sols  the 
particles  are  too  small  for  their  movements  to  be 
observed  in  the  ultra-microscope  (i.e.  they  are  less 
than  about  30  /UL/UL  in  diameter) .  The  ultra-microscope 
is  based  on  the  fact  that  the  existence  of  particles 
which  are  quite  invisible  to  direct  vision  may  be  readily 
recognised  by  passing  a  beam  of  light  across  the  space  in 
which  they  occur.  The  beam  of  light  from  a  lantern 
is  in  itself  invisible,  but  the  particles  of  dust  present 
in  the  air — which  are  also  invisible — reflect  the  light 
in  various  directions,  so  that  we  recognise  the  presence 
of  these  particles  by  their  action  on  the  light. 

Zsigmondy  applies  the  same  principle  to  colloidal 
particles  by  passing  a  very  concentrated  and  powerful 
beam  of  light  horizontally  through  the  liquid  to  be 
examined  and  then  views  the  liquid  against  a  black 
background  through  an  ordinary  microscope.  If  the 
liquid  consists  of  a  solution  of  a  crystalline  salt  the 
field  of  the  microscope  remains  dark,  but  if  an  active 
colloidal  substance  is  substituted  the  field  is  at  once 
occupied  by  minute  specks  of  light  which  dart  hither 
and  thither  in  a  wholly  irregular  manner.  The  ultra- 
microscope  consists  of  a  powerful  source  of  light — an 
arc  lamp  or  the  sun — which  sends  a  beam  of  light 
through  a  suitable  slit  0-002  to  0-02  in.  wide  and  0-004 
to  0-08  in.  high,  the  light  being  focussed  by  a  telescopic 
objective  of  about  0-4  in.  focus.  A  second  similar  lens 
of  about  3  in.  focus  forms  an  image  of  the  slit  in  the 
plane  of  a  condenser,  the  latter  consisting  of  a  micro- 
scope objective,  whereby  a  reduced  image  of  the  slit 
is  thrown  into  the  solution  to  be  examined.  A  polariser 
may  be  inserted  between  the  slit  and  the  second  lens 


if  polarised  light  is  desired,  and  all  extraneous  light 
may  be  cut  off  by  suitably  disposed  diaphragms.  The 
solution  to  be  assayed  is  contained  in  a  specially  shaped 
glass  vessel  termed  a  cuvette,  which  consists  of  an 
accurately  shaped  rectangular  cell  with  a  small  tube 
at  each  end  to  form  an  outlet  and  inlet  respectively. 
By  passing  a  current  of  specially  distilled  water 
through  the  cuvette  it  is  readily  cleaned  and  the  col- 
loidal solution  can  be  admitted,  discharged,  and  the 
cell  washed  as  required. 

FIG.  3.    CUVETTE. 

The  light  passing  horizontally  through  the  solution 
is  reflected  by  suspensoid  particles,  and  if  an  ordi- 
nary microscope  is  used  to  examine  the  solution  in  the 
cuvette  the  field  will  be  illuminated  by  brilliant  specks 
of  light  if  a  colloidal  sol  is  being  examined,  but  will  be 
dark  if  a  crystalloid  solution  is  used.  If  the  cuvette  is 
filled  with  an  active  colloidal  sol,  the  movements  of 
the  particles  are  readily  observable,  and  then  if  to 
this  active  liquid  is  added  another  containing  either 
a  colloid  of  opposite  electrical  sign  or  some  other  sub- 


stance  on  which  the  active  colloid  can  exert  itself,  the 
field  rapidly  darkens  because  the  active  colloid  and 
the  reagent  combine  and  settle  to  the  lower  part  of 
the  cell  and  so  out  of  the  beam  of  light. 

An  active  colloid  which  has,  for  any  reason,  become 
unstable  will  show  very  few  specks  of  light  in  the  ultra- 
microscope,  and  their  movement  will  be  slow  and 
wholly  different  from  a  freshly  prepared  colloid.  By 
this  simple  means,  the  activity  of  a  colloidal  fluid  may 
be  ascertained  in  a  few  minutes  and  all  uncertainties 
in  this  respect  at  once  removed.  Without  such  an 
instrument,  useless,  inactive,  and  unstable  colloidal 
preparations  might  be  administered  instead  of  active 
ones.  The  use  of  an  ultra-microscope  was  particularly 
necessary  when  the  uncertain  colloids  prepared  by 
electrical  methods  or  by  reduction  from  unsuitable 
solutions  were  used,  but  at  that  time,  unfortunately, 
such  instruments  were  not  available  in  this  country. 
During  the  past  five  years,  perfectly  stable  colloidal 
preparations  have  been  available  in  this  country,  and 
as  they  can  be  relied  upon,  if  prepared  by  a  good  firm, 
the  general  use  of  the  ultra-microscope  is  no  longer 

Incidentally,  it  may  be  mentioned  that  the  ultra- 
microscope  has  been  invaluable  in  recognising  the  dis- 
similarity between  normal  and  infected  serum  and  the 
effect  of  prepared  colloids  upon  the  characteristic 
colloidal  eccentricity  of  such  substances  as  syphilitic 
serum.  Normal  serum  is  a  saline  colloidal  solution  of 
insoluble  protein  protected  by  soluble  protein  (aliphatic 
amino-acids).  In  syphilis,  the  proportion  of  colloidal 
matter  in  the  serum  is  supernormal,  and  especially  in 


the  cerebro-spinal  fluid,  and  the  charge  carried  by  the 
protein  is  positive. 

(b)  The  Tyndall  phenomenon  first  investigated  by 
John  Tyndall,1  who  found  that  light  passed  through  a 
gas  or  liquid  containing  particles  in  suspension — even 
when  these  are  so  small  as  to  be  ultra-microscopic— 
produce  a  delicate  blue  colour  the  intensity  of  which 
is  roughly  proportional  to  the  number  of  particles. 
Larger  particles  produce  a  white  tint  as  they  are  not 
small  enough  to  scatter  only  the  shortest  waves  of  light. 

If  a  concentrated  beam  of  light  from  an  arc  lamp  is 
passed  through  a  slit  placed  in  its  focus,  next  through 
the  solution  in  a  rectangular  vessel  and  then  observed 
with  a  mounted  Nicol  prism,  it  will  be  found  that  the 
polarisation  of  the  light  is  affected  by  the  colloidal 
particles.  If  these  are  less  than  100  p.^  in  diameter 
the  polarisation  is  complete,  and  the  Nicol  must  be 
turned  through  90°  to  depolarise  it.  For  larger  ones,  a 
lesser  angle  will  suffice.  If  a  selenite  plate  is  substi- 
tuted for  the  Nicol  prism,  the  light  which  has  been 
polarised  almost  completely  by  the  solution  will  pro- 
duce vivid  colour  effects.  These  coloured  rings  form 
an  extremely  delicate  means  of  estimating  the  number 
of  particles  in  suspension  in  the  solution,  the  diameter 
of  the  beam  of  light  required  to  produce  the  rings  being 
inversely  proportional  to  the  number  of  colloidal 
particles  in  the  solution.  Thus,  a  large  beam  of  light  is 
needed  for  distilled. water,  whilst  with  a  good  colloidal 
solution  so  small  a  beam  as  to  be  scarcely  visible  will 
produce  vivid  colours  with  selenite. 

1  Proc.  Roy.  Soc.  Lond.,  1868,  17,  223  ;  Phil.  Mag.,  1869,  (4),  37, 


A  true  solution  devoid  of  all  colloidal  particles  does 
not  show  the  Tyndall  effect,  though  it  is  extremely 
difficult  to  obtain  any  liquid  which  does  not  give  at 
least  a  faint  indication.  Fluorescent  solutions  (such 





,      4 

'K     I 


1  i 
1  1 

1    H=| 


jT]  i< 



l£J       A\ 

i!      i 


FIG.  4.     TYNDALLMETER  (Vertical  Section  and  Plan). 

as  quinine  disulphate,  dilute  eosin  solution,  etc.)  which 
might  otherwise  be  mistaken  for  colloidal  sols,  do  not 
show  this  effect. 

A  convenient  arrangement  for  applying  the  Tyndall 
beam  to  colloidal  liquids  is  that  devised  by  Tolman 
and  Vliet.  It  consists  of  an  electric  light  bulb  B,  a 


condensing  lens  L,  giving  a  beam  of  parallel  light  which 
passes  through  the  diaphragm  D,  and  a  Macbeth  illu- 
minator for  measuring  the  intensity  of  the  Tyndall 
beam  T.  A  cylindrical  tube  is  introduced  at  T  through 
which  the  liquid  to  be  examined  is  admitted  and  dis- 
charged. The  tubes  Ax  and  A2  are  provided  to  absorb 
the  beam  after  it  has  passed  through  the  colloidal 
liquid,  and  also  to  serve  as  a  dark  ground  on  which  to 
view  the  Tyndall  beam.  The  central  chamber  in  which 
the  colloid  to  be  examined  is  placed  is  about  i  in. 
diameter  and  4  in.  long,  and  the  tubes  Ax  and  A2  are 
about  the  same  diameter  and  12  in.  long.  The  illumi- 
nator is  an  electric  lamp  of  about  3O-candle  power  at  6 
to  8  volts,  capable  of  adjustment  so  that  the  apparatus 
may  be  standardised,  the  light  being  usually  ad- 
justed so  as  to  give  a  brightness  of  22-5  foot  candles, 
though  any  convenient  figure  may  be  used.  The  in- 
tensity of  the  Tyndall  beam  is  fairly  proportional  to 
the  concentration  of  the  colloid  when  the  dispersion 
is  great,  but  when  the  concentration  is  much  higher 
than  0-5  gm.  per  litre  the  intensity  is  not  proportional 
as  the  increased  turpidity  of  the  sol  prevents  the  light 
passing  through  the  liquid.  It  should  be  noted  that 
the  size  of  the  particles  must  be  taken  into  account,  as 
in  the  following  formulae  : 

T=knd*  for  small  particles 
T—klnd6  for  large  particles 

where  T  is  the  intensity  of  the  beam,  k  and  kl  are 
constants  ;  n  is  the  number  of  particles  per  cb.  cm., 
and  d  is  the  diameter  of  the  particles. 

(c)  The  Gold  number  is  a  measure  of  the  protective 


power  of  a  colloid  against  the  tendency  of  other  colloids, 
etc.,  to  effect  precipitation ;  it  is  also  a  measure  of  the 
stability  of  the  colloidal  sol.  The  gold  number  is 
defined  by  Zsigmondy1  as  the  weight  in  mgms.  of 
colloid  which  just  fails  to  prevent  the  change  from 
red  to  violet  in  10  cc.  of  gold  solution  (containing 
0-0053  to  0-0058  per  cent  of  gold)  when  i  cc.  of  10 
per  cent  solution  of  sodium  chloride  is  added  to  the 
sol.  Hence,  the  lower  the  gold  number  the  greater  the 
protective  effect  of  the  colloid  or  the  greater  the 
stability  of  the  sol  examined. 

The  gold  number  is  found  as  follows  :  Three  portions, 
a,  b,  and  c,  containing  0*01,  o-i  and  I  cc.  of  a  suitable 
protecting  colloid  such  as  gelatin  and  i  cc.  of  the  colloid 
to  be  tested,  are  placed  in  three  small  beakers  and  well 
mixed  with  10  cc.  of  gold  collosol.  After  three  minutes 
i  cc.  of  10  per  cent  solution  of  sodium  chloride  is  added 
to  each  and  mixed.  Assuming  there  is  a  colour  change 
in  a  but  not  in  b  the  gold  number  lies  between  o-oi  and 
o-i.  For  a  more  accurate  determination,  repeat  with  a 
fresh  series,  using  0-02,  0-05,  and  0-07  cc.  of  colloid. 
The  following  gold  numbers  are  useful : 

Class  of  protective 

Gelatin  and  glues    .     .     .     0-005-0-010 

Isinglass 0-010-0-020 


Casein          o-oio 

Good  gum  arabic    .     .     .  0-150-0-250  II 

Dextrin 6-000-20-000 1      -QJ 

Potato  starch    .       (about)  25-000 

Silicic  acid oo  IV 

The  stability  number  is  a  useful  modification  of  the 
test,  as  applied  to  the  determination  of  the  stability 

1  Zeits.  anal.  Chem.,  1902,  40,  697. 


of  a  colloidal  sol.  It  is  found  by  first  selecting  a  sub- 
stance which  will  decompose  the  colloidal  sol,  preparing 
a  suitable  solution  of  this  substance,  and  then  adding 
it  to  a  known  volume  of  the  sol  to  be  examined.  The 
amount  of  substance  required  to  just  destroy  the 
activity  of  I  c.c.  of  the  colloidal  sol,  as  observable 
under  the  ultra-microscope,  is  the  stability  number. 

(d)  The  time  required  before  a  colloidal  sol  will  form 
a  deposit  is  a  crude,  but  useful,  measure  of  its  stability. 
With  sols  of  poor  quality  the  time  is  very  short,  but 
properly  stabilised  sols  are  remarkably  durable.    The 
author  kept  a  sample  of  colloidal  iodine  dispersed  in 
33  times  its  weight  of  mineral  oil  for  three  years  and 
found  that  it  was  as  active  and  free  from  deposit  as 
when  first  prepared.    Great  care  is  needed  when  making 
comparisons  of  colloids  on  a  time  basis,  as  so  many 
variable  factors  may  occur.     The  influence  of  heat 
and  light  must  not  be  overlooked,  whilst  even  more 
important  may  be  the  effect  of  traces  of  material  dis- 
solved out  of  the  glass  of  which  the  vessel  containing 
the  colloid  is  composed.     Traces  of  dust  or  organic 
matter  in  the  vessel  used  may  have  a  serious  effect, 
and  for  this  reason  colloidal  sols  should  not  be  stored 
in  corked  bottles.    If  proper  care  is  taken  to  stabilise 
the  sols,  those  used  remedially  can  be  stored  indefi- 
nitely   in    ordinary    glass-stoppered    bottles    as    the 
stabilising  agents  which  prevent  the  decomposition 
of  the  sols  by  silicates  or  alkalies  dissolved  from  the 
glass  do  not  affect  the  physiological  activity  of  the 

(e)  The  effect  of  serum  or  other  physiological  fluids 
on  a  sol  intended  for  medical  or  surgical  purposes 


should  be  fully  investigated  before  employing  the  sol. 
Unless  this  is  done,  sols  may  be  used  which  are  quite 
useless  owing  to  their  premature  decomposition.  This 
applies  particularly  to  "  home-made  "  preparations  ; 
those  bought  from  reliable  manufacturers  have  usually 
been  investigated  by  independent  authorities  and  their 
suitability  can  be  ascertained  by  enquiry.  Speaking 
broadly,  pure  suspensions  of  a  colloid  in  water  are 
quite  useless  physiologically  and  pathologically,  as 
they  are  decomposed  immediately  they  enter  the  blood 
stream.  By  preparing  them  in  a  suitable  manner  with 
the  proper  stabilising  agent  in  each  case,  this  objection 
may  be  completely  overcome. 



IT  has  long  been  the  desire  of  physicians  and  sanitarians 
to  find  a  series  of  substances  which  will  destroy  disease- 
producing  germs  and  yet  prove  harmless  to  human 
beings  or  even  to  domestic  birds  and  animals.  Many 
attempts  have  been  made  to  obtain  compounds 
analogous  to  carbolic  acid,  with  a  high  germicidal  and 
low  toxic  power,  but  only  a  meagre  degree  of  success 
has  been  reached.  This  is  only  to  be  expected  when 
it  is  realised  that  the  human  organism  is  composed  of 
an  indefinite  number  of  cells  and  that  any  substance 
which  kills  bacteria  or  other  disease-producing 
organisms  is  almost  certain  to  have  a  similar  action 
on  these  cells.  The  difference  in  action  is  merely  one 
of  degree,  and  is  therefore  subject  to  limitations  and 
accompanied  by  risks  which  are  far  from  satisfactory. 

Moreover,  some  of  the  most  virulent  germs  are  able 
to  flourish  in  solutions  of  carbolic  acid  (phenol)  and 
other  well-known  disinfectants  of  a  strength  which 
would  be  poisonous  to  human  beings,  and  also  the 
evolution  of  germs  of  one  kind  into  those  of  another 
renders  almost  chimerical  the  search  for  a  general  germ- 
poison  which  is  non-toxic  to  human  beings. 

Fortunately,  the  recognition  of  bacteria  and  their 
products  as  essentially  colloidal  in  character  has  greatly 
facilitated  the  study  of  disinfection.  It  is  now  realised 



that — disregarding  the  fact  that  bacteria  are  alive — 
they  may — owing  to  their  colloidal  character  and  that 
of  the  toxins  and  some  other  substances  they  pro- 
duce— be  destroyed  by  substances  which  bear  an 
electrical  charge  opposite  to  that  of  the  bacteria  or 
their  colloidal  products.  The  effect  of  an  ordinary 
disinfectant  on  bacteria  is  the  result  of  its  adsorption 
by  the  latter,  forming  either  a  chemical  compound,  as 
appears  to  be  the  case  with  formalin,  or  a  distribution 
of  various  phases  in  accordance  with  the  well-known 
law  of  adsorption  of  colloids.  In  the  latter  case, 
colloids  of  opposite  electric  charge  will  precipitate 
each  other  so  long  as  neither  is  in  great  excess,  but  if 
either  colloid  is  in  excess  both  will  be  rendered  inactive 
though  no  precipitation  may  occur. 

The  great  advantage  of  dealing  with  germs  as  colloids 
lies  in  the  fact  that  the  agents  used  for  their  coagula- 
tion and  consequent  destruction  are  not  necessarily 
poisonous — an  advantage  which  becomes  of  utmost  im- 
portance when  it  is  desired  to  destroy  the  bacteria  in 
corpore  villi.  In  other  cases,  where  the  use  of  phenol 
and  other  poisonous  substances  is  less  objectionable, 
their  lower  cost  may  rightly  be  taken  into  considera- 
tion. Some  of  the  most  fruitful  results  in  this  line  of 
research  are  those  which  have  followed  the  discovery 
by  the  late  Henry  Crookes  in  1910  that  certain  metals 
when  in  a  colloidal  state  have  a  highly  germicidal 
action,  but  are  quite  harmless  to  human  beings.  It 
was  previously  known  that  certain  finely  divided 
metals  had  a  feeble  toxic  action  on  the  lower  forms  of 
plant  life,  and  that  the  germicidal  power  of  certain 
metallic  salts  depends  to  a  very  large  extent  on  the 


degree  of  ionisation  and  on  the  specific  properties  of 
the  individual  ions,  those  of  the  metal  having  the 
chief  germicidal  power.  In  other  words,  the  greater 
the  extent  to  which  the  metal  is  set  free  in  a  very 
dilute  solution  of  its  salts,  the  greater  is  the  germicidal 
power  of  the  solution  !  By  converting  the  metal  into 
the  colloidal  state  it  may  be  applied  in  a  much  more 
concentrated  form  and  with  correspondingly  better 

The  importance  of  this  twofold  fact  has  been  largely 
obscured,  partly  by  the  germicidal  properties  of  some 
substances  apart  from  their  degree  of  ionic  dissociation, 
partly  by  the  manner  in  which  some  substances 
are  adsorbed  by  the  products  accompanying  the 
bacteria,  and  so  are  rendered  inert  before  the  latter 
are  affected,  and  partly  because  of  the  ignorance  of 
the  means  of  preparing  colloidal  metals  in  a  form 
sufficiently  stable  for  administration  as  medicines. 

Equally  unfortunate  was  the  death  of  Mr.  Crookes 
before  he  had  been  able  to  extend  the  results  of  his 
discovery,  though  these  difficulties  and  drawbacks 
have  now  been  overcome  and  are  chiefly  of  historical 
interest.  It  is  now  definitely  known  that  the  germi- 
cidal properties  of  certain  colloidal  metals  are  based 
partly  on  the  chemical  action  of  the  metals  themselves, 
different  metals  having  greater  specific  action  on  some 
bacteria  than  on  others,  but  chiefly  on  the  fact  that 
metals  are  in  the  colloidal  (sol)  state. 

These  colloidal  metals — of  which  gold  and  silver 
are  the  best  known — consist  of  such  minute  particles 
that  the  latter  have  ample  space  for  an  extremely 
active  movement  without  touching  one  another. 


Moreover,  by  virtue  of  a  property  well  known  in 
physics — the  particles  having  a  like  electric  charge 
tend  to  repel  one  another  and  thus  increase  the 
stability  of  the  liquid.  When  such  metallic  particles 
are  added  to  a  fluid  containing  in  solution,  suspension, 
or  in  that  intermediate  state  we  recognise  as  colloidal, 
particles  bearing  the  opposite  electrical  charge — or  in 
some  cases  if  the  particles  are  neutral — coagulation 
or  precipitation  rapidly  occurs. 

The  germicidal  action  of  colloidal  metals,  such  as 
silver  and  mercury,  at  a  concentration  of  i  :  20,000 
is  clearly  shown  by  the  following  test  made  by  the 
late  Henry  Crookes  :— 

Silver  and  mercury  "  Collosols "  of  the  normal 
strength  (i  in  2000)  were  diluted  with  9  times  their 
quantity  of  nutrient  broth  (i  in  20,000),  and  10  cc.  of 
this  mixture  were  infected  with  two  loopfuls  of  a 
vigorous  culture  of  B.  coli  communis  ;  after  shaking, 
so  as  to  mix  thoroughly,  streak  cultures  were  made 
quickly  on  agar  plates,  the  first  within  ten  seconds, 
then  at  two,  four,  six,  eight,  and  ten  minute  intervals. 
These  plates  were  incubated  at  37°  C.  for  forty-eight 
hours,  and  gave  the  following  results  :— 

Silver  "  Collosol  "  (i  in  20,000)  Mercury  "  Collosol "  (i  in  20,000) 

with  B.  coli  communis  with  B.  coli  communis 

After  10  seconds — Growth     After  10  seconds — Growth 
2  minutes        „  ,,2  minutes — No  growth 

4  »            »  »  4  »  » 

>,      6  ,,  No  growth  ,,  6  „  „ 

»       o  ,,               ,,  ,,  o  ,,  ,, 

„     10  „                „  „  10 

In  each  case  the  blank  or  control  streak  gave  a  vigorous 


These  experiments  were  repeated  with  silver  and 
mercury  "  Collosols  "  at  the  normal  strength  of  one 
part  in  two  thousand.  In  every  case,  B.  coli  communis 
was  killed  within  ten  seconds,  the  only  growths  on  the 
agar  plates  being  those  of  the  untreated  control 
streaks.  Several  comparative  tests  were  made  with 
the  gonococcus  grown  on  agar  plates  smeared  with 
fresh  blood,  with  the  usual  precautions.  A  plate 
showing  a  vigorous  growth  and  answering  to  the 
typical  tests  (viz.  Gram-negative,  no  growth  on 
gelatin  or  agar  at  20°  C.  without  fresh  blood,  but 
vigorous  growth  at  37°  C.  on  agar  with  fresh  blood, 
and  displaying  the  well-known  diplococcus  in  pus  cells) 
was  swabbed  with  "  Collosol  "  silver  for  two  minutes, 
after  which  time  streak  cultures  were  taken  and 
transplanted  to  agar  plates  smeared  with  fresh  blood 
as  before,  at  intervals  of  two,  four,  six,  eight,  and  ten 
minutes,  and  incubated  in  the  usual  way  at  37°  C. 
Result. — No  growth  whatever. 

Many  series  of  experiments  similar  to  this  gave 
similar  results  ;  for  instance,  a  young  vigorous  growth 
of  B.  tuber colosis  was  killed  by  "  Collosol  "  silver 
(l  in  2000)  in  four  minutes.  Staphylococcus  pyogenes, 
various  Streptococci,  and  other  pathogenic  organisms, 
are  all  killed  in  three  or  four  minutes  ;  in  fact,  no 
microbe  is  known  that  is  not  killed  by  this  colloid  in 
laboratory  experiments  in  six  minutes. 

The  following  experiments  were  made  by  W.  J. 
Simpson,  C.M.G.,  M.D.,  etc.,  Professor  of  Hygiene, 
King's  College,  London,  and  R.  Tanner  Hewlett,  M.D. 
(Lond.),  F.R.C.P.  (Lond.),  Professor  of  Bacteriology  in 
the  University  of  London,  were  printed  in  the 


Lancet  of   12   December,    1914,   and   are   of  special 

Drs.  Simpson  and  Hewlett  mixed  Silver  Collosol 
solution  with  nutrient  broth  in  various  dilutions, 
taking  10  cc.  of  each  in  a  tube.  These  were  inoculated 
with  one  drop  of  24-hour  broth  culture  of  the  typhoid 
bacillus,  incubated,  and  subcultures  made  after  vary- 
ing times.  For  the  sake  of  comparison,  similar  experi- 
ments were  carried  out  with  corrosive  sublimate 
under  the  same  conditions.  The  results  were  as  shown 
in  the  tables  : 


500  per  million 

zoo  „         ,, 

50  „ 

25  „ 

10  „ 

5     „ 

15  min. 

Subcultures  made  after 

30  min.     i  hour      2  hours 

O  O 

tubes  after 
24  hours      3  days 

WITH  CORROSIVE                            Subcultures  made  after 
SUBLIMATE               15  min.      30  min.      i  hour        2  hrs.       24  hrs. 

tubes  after 
3  days 

500  per  million      .      + 



100       ,,             ,,                       + 



50     „                    .      + 

+               000 


25     „                    .      + 

+          o           o          o 


10     „         ,,                + 

+         +         +        + 


5     »         „          •      + 

+          +          +         o 


+   =  growth  ;   o  =no  growth  in  the  subcultures. 

A  comparison  revealing  such  a  small  difference  in 
germicidal  power  between  the  collosol  and  corrosive 
sublimate,  considered  in  the  light  of  the  absolute 
non-toxicity  of  the  collosol,  is  surely  remarkable  and 
cannot  fail  to  evoke  considerable  interest. 

Many  other  experiments  of  a  similar  nature  have 


been  made  by  chemists  and  medical  men,  all  testifying 
to  the  value  of  "  Collosols  "  as  bactericides. 

On  the  2Oth  May,  1913,  two  plates  of  nutrient 
gelatin  were  exposed  on  the  window-sill  for  half  an 
hour.  A  had  been  covered  previously  with  "  Collosol 
Argentum  "  for  five  minutes  ;  B  was  untreated.  Both 
plates  were  incubated  for  forty-eight  hours  at  20°  C.  ; 
after  which,  A  remained  sterile  whilst  B  contained 
about  350  colonies  of  microbes.  Figs.  5  and  6  illustrate 
this  preservative  effect  of  "  Collosol  Argentum." 

It  might  be  suggested  that  a  liquid  containing  only 
one  part  of  colloidal  metal  in  2,000  of  fluid  would  be 
too  weak  to  be  of  use,  but  this  is  not  the  case.  There 
are  at  least  20,000  million  active  particles  of  metal  in 
i  cc.  (=15  drops)  of  properly  prepared  colloidal  silver  of 
this  concentration,  and  one  great  advantage  of  colloidal 
elements  in  such  a  low  concentration  is  their  complete 
harmlessness  to  the  patient. 

Not  all  elements  in  the  colloidal  state  have  a  germi- 
cidal  action.  The  following  table,  based  on  Henry 
Crookes'  investigations,  is  interesting  in  this  connec- 
tion : 

No  germicidal  action :  Gold,  platinum,  palladium, 
rhodium,  indium,  tantalum,  cadium,  magnesium,  tin, 
graphite,  selenium,  sulphur  (sulphur  has  a  strong, 
stimulating  action). 

Slight  germicidal  action  :  Bismuth,  lead,  aluminium, 
zinc,  copper. 

Strong  germicidal  action:  Thorium,  cobalt,  silver, 
mercury,  antimony,  mercuric  cyanide,  mercuric 
chloride,  arsenious  acid. 

The  germicidal  action  of  metals  and  some  other 


substances  is  clearly  shown  in  Figs.  5  to  18,  which  are 
reproduced  from  photographs  taken  by  Hy.  Crookes 
of  Petri  dishes  containing  fish-agar,  or  other  nutrient 
medium  inoculated  with  various  bacteria  and  kept 
under  conditions  favourable  for  their  incubation  and 
development.  In  the  centre  of  each  dish  was  placed  a 
piece  of  the  substance  whose  action  was  to  be  examined 
and  its  effect  is  clearly  shown. 

On  examining  the  illustrations  showing  a  dish  con- 
taining a  germicidal  metal  it  will  be  seen  that  sur- 
rounding the  latter  is  a  vacant  space  in  which  no 
bacteria  have  grown,  around  it  is  a  dense  ring  in  which 
the  germs  have  flourished  to  an  abnormal  degree,  and 
between  this  ring  and  the  circumference  of  the  dish  is 
practically  the  same  as  though  no  germicide  were 
present.  The  cause  of  this  arrangement — which  is 
particularly  marked  in  the  case  of  silver  (Fig.  10) — is 
the  germicidal  action  of  the  minute  amount  of  colloidal 
silver  which  has  been  formed  immediately  around  the 
metal,  whilst  further  away  a  still  smaller  proportion 
of  the  colloidal  silver  has  a  stimulating  action  on  the 
bacteria.  Still  further  away  there  is  no  colloidal  silver, 
and  the  bacteria  grow  in  the  normal  manner.  The 
growth  of  the  same  bacteria  in  the  presence  of  a 
germicidal  and  inert  colloidal  metal  may  be  compared 
by  observing  the  differences  between  Figs.  5,  6  and 
10  ;  the  former,  which  shows  the  action  of  colloidal 
silver,  exhibits  the  characteristic  features  very  clearly  ; 
in  the  latter,  which  shows  the  result  of  using  non- 
germicidal  colloidal  gold,  these  features  are  absent  and 
the  bacterial  growth  is  fairly  uniform. 

The  amount  of  colloidal  metal  produced  under  the 


N    O 






^  U 

c     . 
.2  ffi 

fr          - 


foregoing  experiments  is  almost  infinitesimal,  so  that 
its  germicidal  effect  is  very  striking.  Much  more 
impressive  results  are  obtained  by  the  addition  of  a 
properly  prepared  colloidal  solution  to  an  inoculated 
medium — the  bacteria  then  being  destroyed  quite 
rapidly — but  the  reproduced  photographs  show  in  an 
unmistakably  clear  manner  the  great  potentialities 
of  colloidal  metals  even  under  conditions  which  are 
not  particularly  favourable  to  their  use.  It  has  been 
estimated  that  in  the  death  zone,  where  the  concentra- 
tion of  the  colloidal  metal  is  greatest,  the  latter  does  not 
exceed  twenty-five  parts  per  million  parts  of  nutrient 

The  germicidal  action  of  certain  metals  in  the 
colloidal  state  having  been  demonstrated,  it  only 
remained  to  apply  them  to  the  human  subject,  and 
this  has  been  done  in  a  large  number  of  cases  with 
astonishingly  successful  results.  It  is  not  suggested 
that  colloidal  metal  sols  should  replace  the  customary 
disinfectants  for  sterilising  excreta,  vessels  of  various 
kinds  and  for  other  general  purposes,  but  for  internal 
administration,  either  orally  or  hypodermically,  they 
have  the  advantage  of  being  rapidly  fatal  to  the  para- 
sites— both  bacterial  and  otherwise — without  any  toxic 
action  on  the  host. 



TURNING  now  to  the  use  of  colloidal  liquids  in  the 
relief  or  cure  of  disease,  it  is  important  to  realise  the 
simple  character  of  the  active  agents  in  many  such 
liquids.  In  the  majority  of  the  most  successful 
remedies  definitely  used  on  account  of  their  colloidal 
properties,  the  active  agent  is  a  metal,  such  as  silver, 
mercury,  or  palladium,  or  a  non-metal  element,  such 
as  iodine  or  sulphur.  More  complex  substances,  such 
as  quinine  and  cocaine,  have  also  been  used  success- 
fully in  the  colloidal  state,  but  not  nearly  to  the  same 
extent  as  the  elements  just  mentioned.  The  reason  is 
quite  simple  ;  with  only  a  limited  number  of  investi- 
gators it  is  impossible  to  proceed  as  rapidly  as  may  be 
desirable,  and  the  remarkable  results  which  have 
followed  the  use  of  elements  in  the  colloidal  state  has 
naturally  resulted  in  attention  being  concentrated  on 
these  elements. 

A  great  advantage  which  colloidal  sols  of  elements 
possess  over  compounds  is  the  facility  with  which  their 
action  may  be  studied.  If  a  salt  or  other  compound  is 
administered  there  is  always  the  chance  of  it  under- 
going hydrolysis  or  ionisation  in  the  blood  stream  or 
alimentary  canal,  thereby  setting  up  complex  reactions 
in  which  elements  other  than  the  one  under  investiga- 
tion are  involved.  For  example,  iron  may  be  adminis- 



tered  in  the  form  of  a  carbonate  which  is  converted 
in  the  stomach  into  chloride,  and  this,  on  dilution,  is 
hydrolysed  so  that  eventually  there  are  formed  both 
hydroxide  and  chloride  of  iron.  If  the  iron  were 
administered  as  an  element,  these  complications  would 
be  avoided,  and  the  investigator  would  be  much  more 
certain  in  drawing  conclusions.  Except  in  the  colloidal 
form,  it  is  impossible  to  administer  elements  in  an 
active  state  apart  from  other  elements  necessary  to 
bring  them  into  solution,  for  no  method  of  grinding 
has  been  discovered  which  will  reduce  the  elements  to 
so  fine  a  state  that  they  will  remain  in  suspension  in 
water  for  months  without  any  tendency  to  deposition. 
The  coarser  product  obtained  by  the  most  elaborate 
process  of  trituration  is  devoid  of  those  properties 
which  give  colloidal  sols  their  therapeutic  value. 

The  effect  of  the  administration  of  certain  elements 
in  a  colloidal  state  to  persons  suffering  from  certain 
pathological  conditions  is  extremely  interesting,  partly 
on  account  of  the  progress  of  the  recovery,  and  partly 
on  account  of  the  absence  of  complications  such  as 
occur  when  the  same  element  is  administered  in 
another  form.  For  example,  iodine  and  mercury,  as 
ordinarily  used,  are  both  unsatisfactory  on  account 
of  their  great  toxic  action.  This  is  almost  wholly 
avoided  when  these  elements  are  administered  in  the 
form  of  colloidal  sols.  The  remarkable  fact  that 
colloidal  silver  and  iodine  do  not  stain  the  skin,  whereas 
the  pharmaceutical  preparations  of  silver  and  iodine 
do  so  strongly,  is  a  further  indication  of  the  striking 
difference  between  colloidal  sols  and  ordinary  solutions. 

Widely  as  colloidal  metal  sols  differ  from  the  same 


metals  as  usually  known  and  from  their  salts,  such  sols 
have  a  remarkably  close  resemblance  to  enzymes  in 
their  action  on  physiological  products.  The  activity 
of  both  is  greatly  increased  in  alkaline  solution  up  to  a 
maximum  which  is  followed  by  a  reduction  in  activity 
with  further  increase  in  alkalinity. 

There  is  also  a  striking  parallelism  between  the 
poisoning  action  of  various  substances  (prussic  acid, 
hydrogen  sulphide,  and  mercuric  chloride)  on  a  metal 
sol  and  on  an  enzyme  (p.  42). 

Recent  researches  on  the  action  of  various  glands 
have  also  shown  that  the  fluids  they  excrete  are  not 
only  colloidal  in  character,  but  that  in  several  instances 
they  contain,  as  an  essential  constituent,  some  element 
which  is  not  usually  considered  as  an  integral  part  of 
the  organism.  Thus,  the  dependence  of  the  thyroid 
fluid  on  its  iodine  content  has  only  been  established 
within  the  past  four  years.  In  a  similar  manner  the 
minute  quantities  of  sulphur,  phosphorus,  and  iron 
which  are  present  in  the  animal  organism  are  not 
adventitious.  They  play  definite  parts,  and  their 
absence  or  diminution  results  in  a  serious  disturbance 
of  function.  Insufficient  iodine  in  the  thyroid  gland 
induces  cretinism  and  analogous  diseases,  an  in- 
sufficiency of  phosphorus  accounts  for  certain  nervous 
disorders,  too  little  iron  in  the  blood  results  in  anaemia, 
and  deprivation  of  sulphur  is  characteristic  of  rheu- 
matic subjects. 

The  intense  power  of  reaction  possessed  by  ele- 
mentary sols  is  very  striking.  They  can  induce 
chemical  reactions  to  occur  which  would  otherwise 
require  conditions  of  temperature  and  pressure  quite 


unattainable  in  the  human  subject.  Thus,  metal  sols 
have  a  catalytic  action  as  powerful  as  platinum  black, 
and  can  effect  such  changes  as  the  union  of  hydrogen 
and  oxygen  in  the  cold,  the  oxidation  of  hydriodic  acid 
by  oxygen  in  solution,  and  the  decomposition  of 
hydrogen  dioxide. 

The  activity  of  some  metal  sols  is  so  great  as  to  be 
barely  conceivable.  Thus,  platinum  sol  has  marked 
catalytic  properties  when  only  0-0000002  grain  of  the 
metal  is  present !  This  intense  power  of  promoting 
reactions  among  other  substances  and  of  being  them- 
selves left  free  at  the  end  of  the  reaction  results  in 
very  small  quantities  of  metal  sols  being  capable  of 
effecting  changes  which  are  wholly  disproportionate 
to  the  amount  of  sol  present.  It  also  explains  why 
changes  which  are  of  an  extremely  complex  character 
when  a  catalyst  is  absent  may  be  effected  readily  in 
the  presence  of  an  elemental  sol,  and,  further,  that  the 
administration  of  such  a  sol  will  produce  results  in  a 
short  time  which  would  require  a  long  period  if  effected 
by  means  of  a  long  series  of  successive  reactions. 
Metal  sols  have  the  further  therapeutic  advantage  of 
acting  most  rapidly  in  faintly  alkaline  solutions,  so  that 
when  properly  prepared  they  are  not  affected  adversely 
by  normal  blood. 

Before  a  drug  can  exert  its  full  therapeutic  action  it 
must  be  converted  into  the  ionised  or  into  the  colloidal 
state.  Unfortunately,  an  element  in  the  ionised  state 
is  always  associated  with  the  corresponding  ions  of  the 
salt  from  which  it  was  produced.  Thus,  mercuric 
chloride,  when  ionised,  is  separated  into  mercury  ions 
and  chlorine  ions,  and  the  net  electric  charge  of  the 


system  is  neutralised.  When  an  element  such  as 
mercury  is  administered  in  the  colloidal  state,  however, 
it,  and  it  alone,  is  introduced  as  an  active  agent,  the 
charge  on  the  particles  is  quite  definite  and  their 
activity  is  correspondingly  great.  Consequently,  there 
is  much  truth  in  the  statement  that  a  drug  to  be  fully 
efficient  must  be  in  a  colloidal  state,  or  convertible 
into  it  in  the  body  of  the  subject. 

The  conversion  of  a  colloid  into  the  form  required 
by  the  organism  is  most  rapid  when  the  sol  is  injected 
intramuscularly,  but  there  is  less  pain  and  equally 
good  (though  slower)  results  by  intravenous  injections, 
and  in  many  cases  by  oral  administration. 

The  use  of  specific  sols  in  medicine  is  no  universal 
"  cure  all,"  but  just  as  the  administration  of  pure 
chemicals,  such  as  quinine  hydrochloride,  marked  a 
great  advance  over  the  use  of  a  crude  tincture  of 
cinchona  bark,  so  the  employment  of  certain  elements 
in  the  form  of  sols  marks  a  still  further  line  of  progress 
in  the  conquest  of  disease. 

Taking  the  chief  colloidal  sols  which  have  been 
used  medicinally,  we  may  first  mention  several  metal 
sols  : 

Colloidal  gold  was  first  prepared  in  a  sufficiently  pure 
state  for  effective  examination  by  Faraday  in  1857, 
but  it  was  known  in  the  Middle  Ages,  though  its  most 
important  properties  were  not  realised.  As  early  as 
1885,  it  was  largely  in  use  in  the  United  States  as  the 
basis  of  a  cure  for  dipsomania,  but  even  then  it  was 
only  one  of  a  number  of  ingredients  of  a  complex 
mixture  whose  manufacturer  does  not  appear  to  have 
known  much  about  the  properties  of  the  gold  in  his 


preparation,  notwithstanding  the  statements  in  the 
advertisements  of  that  day. 

Colloidal  gold  is  characterised  by  the  great  differ- 
ence in  its  colour  when  it  is  prepared  by  different 
methods.  As  ordinarily  prepared  by  reducing  a 
slightly  alkaline  solution  of  gold  chloride  with  formal- 
dehyde or  phosphorus,  it  is  an  intensely  red  liquid,  the 
particles  of  which  are  negatively  charged,  but  by  the 
addition  of  suitable  electrolytes  (aluminium  salts),  it 
is  also  possible  to  produce  a  blue  solution  with  posi- 
tively charged  particles.  A  colourless  gold  sol  is 
produced  if  the  electric  field  is  too  strongly  negative 
or  positive.  Experiments  by  Garnet l  on  the  refractive 
indices  of  colloidal  sols  of  gold,  silver,  and  copper  show 
that  the  metal  in  each  case  is  in  suspension  in  the  form 
of  extremely  minute  spheres  and  that  the  different 
colours  of  gold  sols  are  due  to  the  particles  of  metal 
and  not  to  any  inherent  differences  in  the  nature  of  the 
dispersed  particles.2 

Colloidal  gold  sol  is  tasteless  and  non-poisonous,  but 
the  metal  is  readily  precipitated  by  bases  and  salts, 
so  that  it  is  not  easy  to  administer  it  satisfactorily. 
Moreover,  the  germicidal  action  of  gold  is  very  feeble 
(p.  73),  so  that  its  use  in  therapeutics  is  negligible. 
On  the  other  hand,  it  is  so  easily  prepared  and  is  so 
highly  sensitive  that  gold  sol  is  chiefly  used  as  a 
standard  with  which  others  may  be  compared. 

1  Phil.  Trans.,  (A)  203,  1904,  385  ;   and  205,  1906,  237. 

z  According  to  T.  Sherrer  (Engineering,  1919,  488),  colloidal  gold 
and  silver  hydrosols,  when  examined  by  X-rays,  show  interference 
bands  characteristic  of  crystalline  solutions  ;  the  interference  bands 
of  the  hydrosols  of  silica  and  stannic  acid  show  that  these  substances 
are  sometimes  crystalline  and  sometimes  amorphous.  Colloidal 
albumen,  casein,  starch,  and  cellulose  appear  to  be  always  amorphous. 


Colloidal  silver,  containing  0-05  per  cent  of  the 
metal  in  a  colloidal  form  and  not  as  a  salt,  is  a  clear 
cherry  red  liquid  which  possesses  a  marked  oxidising 
action  in  addition  to  its  power  of  coagulating  colloids 
of  opposite  electric  sign. 

The  colour  of  the  pure  silver  sol  is  largely  dependent 
on  the  manner  of  its  preparation  and  the  presence  or 
absence  of  minute  quantities  of  electrolytes.  Even 
the  glass  of  the  vessel  in  which  the  sol  is  prepared  may 
affect  the  colour  by  yielding  traces  of  soda,  silica,  or 
other  oxide  to  the  sol.  When  prepared  under  suitable 
conditions  and  properly  "  protected,"  colloidal  silver 
sol  is  quite  stable  even  in  the  presence  of  salts  and  of 
the  normal  constituents  of  the  blood.  Its  destructive 
action  on  toxins  is  very  marked,  so  that  it  will  protect 
rabbits  from  ten  times  the  lethal  dose  of  tetanic  or 
diphtheric  toxin.  Colloidal  silver  is  prepared  in  the 
following  forms  to  meet  clinical  requirements  : 

(a)  Aqueous  solution,  in  bottles  or  ampoules. 

(b)  Pasta,  in  glyco-gelatin  base. 

(c)  Ointment  in  lanoline  base. 

(d)  Suppositories  and  pessaries. 

Unlike  certain  organic  compounds  of  silver,  the 
colloidal  metal  is  not  organotropic  and  does  not  cause 
necrosis  of  the  underlying  tissues.  Hence,  it  has  been 
used  for  several  months  consecutively  without  staining 
the  conjunctiva.1 

Taken  internally,  the  particles  of  colloidal  silver  are 
resistant  to  the  action  of  dilute  acids  and  alkalies  of 
the  stomach,  and  consequently  continue  their  catalytic 
action  and  pass  into  the  intestine  unchanged.  The 

*  Brit.  Med.  Jaurn.,  Jan.  15,  1915. 


importance  of  this  is  obvious  in  such  conditions  as 
ulcerative  urticaria  and  other  forms  of  dermatitis  sug- 
gestive of  toxaemia,1  bacillary  dysentery,  diarrhoea,  and 

The  use  of  collosol  argentum  in  ophthalmic  practice2 
and  in  the  affections  of  the  ear  and  in  nasal  catarrh3 
and  its  clinical  effect  by  intravenous  injection  in 
septicaemia  are  reported  in  the  medical  journals.4 

Colloidal  silver  has  been  used  with  marked  success 
in  the  following  cases,  cited  by  C.  E.  A.  MacLeod5 : 

Septic  and  follicular  tonsilitis,  Vincent's  angina, 
phlyctenular  conjunctivitis,  gonorrhceal  conjunctivitis, 
spring  catarrh,  impetigo  (contagious  acne  of  face  and 
body),  septic  ulcers  of  legs,  ringworm  of  body,  tinea 
versicolor,  soft  sores,  suppurative  appendicitis  after 
operation  (the  wounds  cleaned  rapidly),  pustular 
eczema  of  scalp  and  pubes,  chronic  eczema  of  meatus 
of  ear  with  recurrent  boils,  and  also  chronic  eczema  of 
anterior  nares,  offensive  discharge  in  case  of  chronic 
suppuration  in  otitis  media,  bromidrosis  of  feet,  axillae 
and  blind  boils  of  neck.  By  injection  :  gonorrhoea 
and  chronic  cystitis  (local),  boils,  epiditymitis. 

Sir  James  Cantlie6  has  found  it  particularly  effective 
in  cases  of  sprue,  dysentery,  and  intestinal  troubles. 
Being  non-toxic,  the  dose  can  be  increased  from  i  to  2 
or  more  drachms  twice  or  thrice  daily. 

A.  Legge  Roe  regards  stable  colloidal  silver  as  a 
most  useful  preparation7  in  ophthalmic  practice,  and 
particularly  in  cases  of  gonorrhceal  ophthalmia,  puru- 

1  Brit.  Med.  J.,  May  12,  1917.  •  Lancet,  Feb.  3,  1912. 

2  Brit.  Med.  J.,  Jan.  15,  1917.  8  Brit. Med.  J., Nov.  15,1913. 
8  Brit.  Med.  J.,  Dec.  15,  1917.  7  Brit.  Med.J.,  Jan.  16, 1915. 
*  Lancet,  Feb.  16,  1918. 


lent  ophthalmia  of  infants,  infected  ulcers  of  the  cornea 
and  hypopyon  ulcer  (tapping  of  the  interior  chamber 
and  cautery,  and  other  operative  procedures  being  now 
rarely  required,  whilst  if  perforation  does  occur  it  is 
smaller  and  more  manageable),  interstitial  keratitis, 
blepharitis,  dacryocystitis,  and  burns  and  other  wounds 
of  the  cornea.  According  to  this  authority,  the  great 
chemosis  which  usually  accompanies  the  use  of  silver 
nitrate  is  avoided  and,  in  his  opinion,  if  colloidal  silver 
were  adopted  in  every  case  of  purulent  ophthalmia 
of  infants  "  there  would  be  no  such  thing  as  impaired 
sight  or  blindness  from  this  cause."  He  has  had  many 
cases  of  interstitial  keratitis  in  adults,  in  which  the 
complete  opacity  of  the  cornea  has  become  absolutely 
clear  in  from  three  to  five  months,  and  anyone  who  has 
had  much  experience  of  this  disease  in  adults  knows 
how  often  permanent  impairment  of  sight  results,  and 
how  long  the  treatment  used  to  last,  especially  if 
irritants  had  been  used  prior  to  colloidal  treatment 
The  eye  is  kept  under  atropine  or  preferably  scopola- 
mine,  and  the  colloidal  sol  is  dropped  in  three  times  a 
day,  the  eye  being  kept  closed  afterwards  for  five 
minutes.  When  all  active  symptoms  have  disappeared, 
and  not  until  then  if  any  opacity  remains,  yellow  oxide 
or  mercury  ointment  may  be  used ;  but,  if  treated 
throughout  as  described  above,  this  will  rarely  be  neces- 
sary. In  dacyocystitis,  Dr.  Roe  recommends  that 
"  after  probing,  the  sac  should  first  be  syringed  out 
with  saline  solution  and,  after  expressing  any  that 
remains,  the  sac  should  be  filled  with  colloidal  silver 
with  the  syringe.  In  cases  of  long  standing  this  will 
not  be  sufficient ;  the  sac  should  be  incised  and  plugged 


with  ribbon  gauze,  and  for  about  a  week  the  sac  should 
be  dressed  daily  by  inserting  it  into  ribbon  gauze 
soaked  in  10  per  cent  solution  of  potassium  bichromate, 
or  the  lining  membrane  of  the  sac  should  be  scraped. 
The  wound  is  then  allowed  to  close  and  the  collosol 
injections  continued." 

T.  H.  Anderson  Wells1  used  it  intravenously  in  a 
case  of  puerperal  septicaemia  without  any  irritation  of 
the  kidneys  and  with  no  pigmentation  of  the  skin. 
This  physician  has  found  that  a  series  of  intravenous 
injections,  each  of  collosol  argentum,  every  forty-eight 
hours  produce  no  untoward  effects  and  that  recovery 
is  rapid. 

Sir  Malcolm  Morris2  has  found  that  colloidal  silver 
is  free  from  the  drawbacks  of  other  preparations  of 
silver,  viz.  the  pain  caused  and  the  discoloration  of 
the  skin  ;  indeed,  instead  of  producing  irritation  it 
has  a  distinctly  soothing  effect.  It  rapidly  subdues 
inflammation  and  promotes  the  healing  of  the  lesions. 
He  has  had  remarkable  results  in  enlarged  prostate 
with  irritation  of  the  bladder,  in  pruritis  ani  and 
perineal  eczema,  and  in  haemorrhoids.  It  can  be  used 
in  the  form  of  suppositories  whilst  a  solution  is  simul- 
taneously applied  to  the  irritated  skin.  In  bromidrosis 
in  the  axillae  and  feet  it  quickly  gives  relief.  It  causes 
a  rapid  disappearance  of  warts.  Being  non-toxic,  it 
can  be  given  internally  in  urticaria  and  other  forms  of 
dermatitis  which  are  suggestive  of  toxaemia.  In  such 
cases,  it  is  quickly  beneficial. 

In  ophthalmology,  colloidal  silver  has  now  largely 
replaced  silver  nitrate. 

1  Lancet,  Feb.  16, 1918.  2  Brit.  Med.  J.,  May  12, 1917. 


J.  Mark  Ho  veil1  has  found  colloidal  silver  beneficial 
for  permanently  restoring  the  potency  of  the  Eusta- 
chian  tubes  and  for  reducing  nasopharyngeal  catarrh. 

Colloidal  silver  has  also  been  used  successfully  in 
septic  conditions  of  the  mouth  (including  pyorrhoea 
alveolaris — Rigg's  disease),  throat  (including  tonsilitis 
and  quinsies),  ear  (including  Menier's  symptoms  and 
closure  to  Valsava's  inflation),  and  in  generalised  septi- 
caemia, leucorrhcea,  cystitis,  whooping-cough,  and 

A  preparation  of  colloidal  silver  which  is  opaque  to 
X-rays  has  proved  invaluable  in  certain  diagnoses. 

J.  MacMunn 2  has  successfully  used  silver  sol  in  cases 
of  gonorrhceal  prostatic  gleet  by  injecting  through  an 
endoscope  into  the  substance  of  the  prostate  gland. 

Collosol  argentum  has  also  proved  useful  in  influenza, 
both  as  a  prophylactic  and  for  curative  purposes  when 
applied  as  a  spray  to  the  nostrils,  for  bathing  the  eyes, 
and  as  a  gargle  for  the  throat. 

B.  Seymour  Jones  has  used  an  intranasal  spray  of 
colloidal  silver  in  a  case  of  cerebro-spinal  meningitis. 
He  has  also  used  colloidal  silver  with  marked  advan- 
tage in  several  cases  of  rhinitis  and  cedematous  en- 
largement of  the  posterior  ends  of  the  middle  and 
inferior  turbinates  without  true  hyperplasia. 

Colloidal  mercury  is  quite  free  from  the  serious  objec- 
tions to  the  less  soluble  mercury  salts — such  as  calomel 
—the  delayed  and  irregular  absorption  with  conse- 
quent undesirable  results  of  other  preparations  and, 
unlike  the  soluble  mercury  salts,  it  is  only  feebly  toxic. 

1  Brit.  Med.  Journ.,  Dec.  15,  1917. 
1  Brit.  Med.  Journ.,  1917,  I,  685. 


§  8 

«  § 

S  u 


With  colloidal  mercury,  the  diffusion  is  extremely  rapid 
and  chemical  affinity  low.  Hence,  the  toxicity  of  col- 
loidal mercury  (1-2000)  is  so  low  that  doses  of  two 
teaspoonfuls  may  be  taken  twice  daily  or  intravenous 
injections  of  30  cc.  may  be  given  with  impunity. 

Intravenous  injections  of  colloidal  mercury  are  pain- 
less, and  this  absence  of  pain  is  usual  in  the  adminis- 
tration of  colloidal  preparations,  and  is  due  to  their 
isomorphism  with  the  colloidal  lipoid  and  protein  of 
the  tissues  and  body  fluids.  Before  the  introduction 
of  the  arseno-benzene  products,  the  routine  treatment 
for  syphilis  was  mercury  and  iodides,  and  undoubtedly 
many  permanent  and  excellent  results  were  obtained. 

In  late  syphilis,  iodine  is  more  effective  than  mercury, 
and,  conversely,  mercury  is  more  effective  than  iodine  in 
early  syphilis.  According  to  J.  E.  R.  McDonagh,1  this  is 
due  to  the  fact  that  mercury  acts  as  an  oxidising  agent 
and  that  the  process  of  oxidation  is  more  effective  in  the 
early  stages  of  syphilis  in  producing  the  death  of  the 
causal  organism,  whilst  as  a  reducing  agent  it  is  more 
effective  in  the  later  stages.  In  most  cases,  the  alter- 
nate injection  of  colloidal  iodine  and  mercury  is  more 
effective  than  if  either  be  given  continuously.  Accord- 
ing to  J.  E.  R.  McDonagh,2  the  first  effect  of  injecting 
a  suitable  colloid  is  to  break  large  protein  particles  into 
small  ones  and  thus  increase  their  activity  by  enlarging 
their  surface  area.  In  syphilis,  there  are  many  large 
particles  to  be  broken  up,  hence  the  value  of  colloid 
sols.  The  injection  of  colloid  sols  also  affects  the  state 
of  oxidation  or  reduction  of  the  system  in  which  it  is 
introduced,  metallic  sols  increasing  the  oxidation  and 

1  Prescriber,  June,  1919,  118-120.      *  Brit.  Med.  J.t  1917,  I.  648, 


non-metallic  sols  the  reduction.    Colloidal  mercury  has 
cured  persistent  relapsing  malaria  in  a  few  days.1 

Colloidal  iron  is  the  least  irritating  of  all  forms  of 
iron,  yet,  according  to  Lyn  Dimond,2  it  kills  within  six 
minutes  such  organisms  as  B.typhosus,  B.  coli  communis, 
and  various  pyogenic  cocci.  The  iron  sol  seems  to  have 
a  definite  elective  bactericidal  action  upon  such  catarrh- 
causing  organisms  as  the  pneumococcus  and  various 
strains  of  the  Micrococcus  catarrhalis.  Rapid  relief 
follows  the  topical  application  of  colloidal  iron  in  cases 
of  catarrh  of  the  nose,  larynx,  or  pharynx. 

It  is  also  used  by  subcutaneous,  intramuscular  and 
intravenous  injection  in  cases  of  extreme  chlorosis, 
anaemia,  erysipelas,  and  cellulitis. 

Iron  is  almost  the  only  metal  found  in  the  animal 
organism  which  is  also  obtainable  in  a  colloid  state  in 
the  presence  of  water.  The  significance  of  the  fact  has 
not  been  sufficiently  recognised.  In  the  serum,  the  iron 
is  probably  present  as  a  protein  compound,  the  precise 
constitution  of  which  has  not  been  determined.  Some 
authorities  consider  that  the  whole  of  the  iron  exists 
in  the  form  of  haemoglobin.  The  total  iron  content 
of  the  normal  body  does  not  exceed  thirty-seven  grains, 
and  although  several  organic  compounds  of  iron  have 
been  recommended  they  are  by  no  means  satisfactory, 
being  either  too  feeble  in  action  or  too  readily  decom- 
posed in  corpore  and  so  rendered  useless.  Inorganic 
iron  is  held  by  many  practitioners  to  be  most  efficient 
in  the  only  true  test  of  the  value  of  an  iron  preparation, 
i.e.  increase  of  haemoglobin  in  the  blood.  Haemoglobin 

1  G.  Cremonese,  Garr,  D.  Osp.,  1918,  39,  427. 

2  Lancet.  1913,  I,  1585. 


was  at  one  time  thought  to  be  a  definite  compound, 
but  its  adsorption  properties  seem  to  show  that  it  is 
largely  colloid  in  character  and  consequently  is  specially 
amenable  to  the  action  of  another  colloid  such  as  iron. 
Haemoglobin  is  electro-positive,  and  to  increase  its 
amount  without  disturbing  the  general  characteristics 
of  the  serum  any  iron  compound  administered  must  be 
electro-positive  when  it  enters  the  blood  stream.  For 
this  reason,  iron  compounds  (e.g.  ferric  chloride)  which 
are  electro-negative  and  act  as  coagulants  should  be 
avoided.  The  objection  to  iron  carbonate  and 
hydroxide  lies  in  the  fact  that  they  are  usually  con- 
verted into  ferric  chloride  or  analogous  compounds  by 
the  gastric  juices. 

Colloidal  iron,  on  the  contrary,  not  being  affected  by 
these  juices,  is  able  to  enter  the  blood  stream  in  a  satis- 
factory and  therapeutically  active  form.  Hence  the' 
administration  of  iron  in  the  form  of  a  colloidal  sol 
appears  to  be  a  simple  means  of  increasing  the  amount 
of  the  protein  compound  in  the  serum,  as  this  form  of 
iron,  when  administered  orally,  is  rapidly  diffused  in  the 
stomach,  and  yet  it  is  not  absorbed  in  individual 
positions.  It  is  found  that  the  amino-acids  formed 
during  the  process  of  digestion  are  readily  able  to  absorb 
into  their  complex  molecule  a  notable  proportion  of 
iron  administered  in  the  colloidal  form,  and  from  it 
to  effect  the  synthesis  of  haemoglobin. 

Colloidal  antimony  has  been  used  with  remarkable 
and  surprising  results  in  the  treatment  of  coccogenic 
skin  disease,  including  deep  abscesses,  boils,  and  deep- 
seated  impetigo.  It  has  also  been  successfully  used  by 
intramuscular  injection  in  bilharzia,  leishmonnoris, 


granulama  pupendi,  ulcus  molle  serpiginosum,  and  in 
certain  stubborn  cases  of  gonococcal  urethritis. 

Colloidal  antimony  has  been  used  in  conjunction 
with  manganese  with  extremely  good  results  in  gono- 
coccic  infections.  In  India,  it  has  given  very  satisfac- 
tory results  in  Kala-azar,  its  administration  in  this 
disease  being  accompanied  with  less  risk  than  that  of 

Colloidal  manganese  has  been  used  with  remarkable 
and  surprising  results  in  the  treatment  of  coccogenic 
skin  disease,  including  deep  abscesses,  boils,  and  deep- 
seated  impetigo.  In  superficial  impetigo,  chronic 
seborrhoeic  eczema,  and  acute  folliculitis  it  is  of  little 
value  when  used  alone,  but  it  gives  excellent  results 
when  employed  in  conjunction  with  intramine.  The 
rapidity  of  its  action,1  combined  with  the  saving  of 
dressings,  render  the  use  of  this  form  of  manganese 
very  attractive  in  deep-seated  coccogenic  lesions.  It 
is  usually  injected  intramuscularly  in  amounts  of  3  cc. 
every  few  days.  In  most  cases,  one  injection  is  suffi- 
cient. Indeed,  colloidal  manganese  differs  from  all 
other  remedies  used  in  the  treatment  of  boils,  insomuch 
as  it  is  only  occasionally  that  fresh  boils  make  their 
appearance  during  the  treatment,  and  these  quickly 
subside  without  further  trouble. 

E.  W.  Kirk2  and  Dr.  W.  Habgood3  found  colloidal 
manganese  so  good  as  to  convince  them  that  it  should 
have  a  wider  use  in  furunculosis  and  seborrhoeic  eczema 
following  wound  infection,  and  W.  E.  Levinson4  has 

1  J.  E.  R.  McDonagh,  Medical  Press  and  Circular,  Dec.  5,  1917; 
Sir  Malcolm  Morris,  Brit.  Med.  Journ.,  April  26,  1918. 

2  Brit.  Med.  Journ.,  1918,  II,  377.       3  Brit.  Med.  Journ.,  II,  76. 
*  Brit.  Med.  Journ.,  1918,  II,  160. 




I * 



confirmed  Sir  Malcolm  Morris's1  recommendation  of 
colloidal  manganese  for  boils. 

J.  E.  R.  McDonagh2  has  also  used  intravenous  injec- 
tions of  33  cc.  of  colloidal  manganese  with  excellent 
results  in  cases  of  poisoning  by  sulphur  compounds, 
including  mustard  gas  (dichlorethyl  sulphide).  Three 
typical  cases  reported  by  Sir  Malcolm  Morris  are,  in  his 
opinion,  so  remarkable  as  to  demand  publication.  At 
first  the  collosol  manganese  (Crookes)  was  used  in  the 
form  of  a  single  solution.  Afterwards  it  was  employed 
in  the  improved  form  of  two  solutions,  which  were 
mixed  in  the  syringe  ;  of  this,  much  smaller  doses 
(about  one-half)  suffice. 


"  The  patient,  a  medical  man,  came  to  me  on  Novem- 
ber 24th,  1917,  with  large,  deep-seated  boils  on  the 
hairy  part  of  the  face,  which  he  believed  to  be  an 
infection  from  a  carbuncle  in  a  diabetic  patient,  from 
whom  he  had  contracted  a  septic  whitlow.  Culture 
showed  that  the  micro-organism  was  the  Staphylococcus 
pyogenes  aureus,  and  an  autogenous  vaccine  was  pre- 
pared, with  which  he  was  inoculated  on  November  3Oth. 
By  this  time  a  boil  on  the  right  cheek  had  enlarged  to 
the  size  of  a  Tangerine  orange  ;  there  was  much  cedema 
of  the  face  and  eyelids  and  great  pain.  On  December 
6th  pus  was  discharged  and  the  pain  relieved ;  but 
during  the  next  seven  weeks  boils  continued  to  appear 
at  intervals,  usually  in  groups  of  four  or  five,  on  one 
or  both  sides  of  the  face.  By  January  I4th,  eleven  in- 
jections of  vaccine  had  been  given,  antiseptic  lotions 

1  Brit.  Med.  Journ.,  1918,  I,  446. 

*  J.  E.  R.  McDonagh,  Medical  World,  1918,  p.  137. 


and  ointments  being  also  applied.  On  January  3ist 
the  patient  consulted  me  again  and  I  advised  the  in- 
jection of  collosol  manganese.  The  first  injection  was 
given  the  next  day.  '  Improvement,'  to  quote  from 
the  patient's  own  notes,  '  began  on  the  third  day 
afterwards.  Subsequent  boils,  which  continued  to 
appear  for  a  further  fourteen  days,  were  not  painful, 
and  many  of  them  aborted  without  pus  formation.'  In 
all,  four  injections  were  given — 1-5  on  January 
3ist,  2-5  on  February  5th,  3  on  February 
I2th,  and  i  on  February  28th  ;  the  first  and 
second  in  the  gluteus,  the  third  and  fourth  in  the  flank. 
In  the  first  three  the  old  preparation  was  used  ;  in  the 
fourth  the  new.  By  March  5th  I  was  able  to  report 
'  All  clear/  From  November  3oth  to  January  3ist, 
while  the  vaccine  was  being  given,  thirty-three  carbun- 
cular  boils  appeared  ;  after  the  collosol  manganese  was 
begun  there  were  only  seven,  the  last  appearing  on 
February  2Oth,  three  weeks  after  this  treatment  was 
begun.  The  patient's  general  health  also  greatly 
improved  ;  he  began  to  feel  better  within  a  week  of 
the  first  manganese  injection." 


"  The  patient  was  an  army  captain  who  was  subject 
to  acne.  When  the  first  collosol  manganese  injection 
(0-5  of  the  new  preparation)  was  given  on  March 
I3th,  he  had  been  in  hospital  four  months  with  facial 
boils  and  acute  impetigo  contagiosa  of  the  same  region. 
During  that  time  he  had  had  vaccine  injections,  and 
various  antiseptics  had  been  applied,  without  result. 


Another  manganese  injection  (0-5  was  given  on 
March  i6th,  and  a  third  (i  on  March  igth.  By 
this  time  all  the  lesions  had  cleared  up." 


"  I  saw  the  patient,  a  lady,  for  the  first  time  on 
February  i6th.  She  had  extensive  follicular  impetigo 
of  the  scalp,  which  began  in  the  preceding  October, 
and  had  gradually  become  more  severe.  When  she 
came  to  me,  she  complained  of  great  pain  from  small 
multiple  deep  abscesses.  There  was  a  good  deal  of 
oedema,  and  the  posterior  cervical  glands  were  enlarged. 
On  February  i8th  1-5  of  the  old  collosol  man- 
ganese solution  was  injected.  By  February  22nd  the 
lesions  were  beginning  to  clear  up,  the  pain  was  nearly 
gone,  and  the  general  health  distinctly  better.  A 
second  injection  (0-5  of  the  new  preparation) 
was  given,  and  a  third  (i  three  days  later.  By 
this  time  further  improvement  was  manifest,  and  the 
patient  was  able  to  sleep.  No  further  injection  was 
required,  and  by  March  igth  recovery  was  complete, 
the  only  trace  of  the  disease  consisting  in  small  bald 
areas  on  the  site  of  the  lesions." 

Sir  Malcolm  Morris  attaches  much  importance  to 
the  great  improvement  in  the  patient's  general  health 
observable  in  each  case  a  few  days  after  the  first  injec- 
tion, and  the  fact  that  although  the  injections  were 
all  intramuscular  they  were  followed  by  no  reaction. 

D.  McFarland  Livingstone  has  used  colloidal  man- 
ganese with  great  advantage  in  three  cases  of  gonorr- 
hceal  ophthalmia.  The  first  was  not  of  great  severity, 
but  the  drug  was  satisfactory.  In  the  second  case, 


corneal  ulceration  had  set  in,  but  the  eye  healed 
rapidly.  The  third  case  was  of  the  most  virulent 
type,  and  the  effect  of  colloidal  manganese  was  most 
striking.  Prior  to  treatment,  both  eyelids  were  greatly 
swollen  and  almost  solid  ;  there  was  great  tenderness 
and  pain  and  the  surrounding  cheek  was  also  red  and 
swollen.  On  opening  the  lids,  the  cornea  was  found  to 
be  completely  hidden  by  overlapping  folds  of  cedema- 
tous  bulbar  conjunctiva.  There  was  an  abundant  dis- 
charge of  pus.  The  eye  was  bathed  with  warm  boric 
lotion  and  argyrol  was  used  every  six  hours.  An  in- 
jection of  colloidal  manganese  was  given  intra-mus- 
cularly  into  the  buttock.  On  the  second  day  there  was  a 
slight  improvement.  On  the  third  day  there  was  slight 
pain  ;  on  the  fourth  day  a  second  injection  of  i  cc.  of 
colloidal  manganese  was  given,  and  by  the  following 
morning  all  pain  had  ceased,  all  the  swelling  of  the  bulbar 
conjunctiva  had  completely  vanished,  the  oedema  had 
lessened,  and  the  discharge  was  considerably  reduced. 
The  cornea  was  perfectly  clear,  and  the  eye  was  ap- 
parently out  of  danger.  After  one  week  from  the 
first  injection,  a  third  and  last  injection  of  manganese 
was  given,  and  after  a  further  week  the  eyes  had 
become  normal,  except  for  gumming  of  the  eyelids 
after  sleep.  Dr.  Livingstone  reports  of  this  case  that 
"  in  a  fairly  wide  and  long  experience  in  the  treatment 
of  gonorrhceal  blenorrhcea  it  had  never  been  my  good 
fortune  to  witness  such  a  dramatic  change.  No  local 
measures  of  which  I  am  acquainted  would  have  brought 
about  such  a  satisfactory  termination." 

It  is  not  suggested  that  undue  importance  should 
be  attached  to  a  single  case,  however  striking,  yet  it  is 




clear  that  such  a  good  indication  of  what  may  be 
expected  under  similar  conditions  should  not  pass 

Colloidal  manganese  has  also  been  used  successfully 
in  the  case  of  toothache  due  to  abscess.1 

Colloidal  copper  sols  are  blue,  red,  orange,  or  green, 
according  to  the  conditions  under  which  they  are 
prepared,  and  the  agent  used  to  stabilise  them. 
Thus,  if  protalbinic  acid  followed  by  hydrazine 
is  used  for  reducing  copper  sulphate,  the  sol  is  red 
or  orange,  whilst  with  protalbinic  acid  and  sodium 
chloride  Paal  obtained  green  copper  sols.  Copper 
has  a  special  action  on  the  liver  and  is  well  known 
as  a  fungicide  and  as  restraining  the  growth  of  the 
lower  organisms  and  embryonic  cells.  In  the  form 
which  has  given  the  best  therapeutic  results,  col- 
loidal copper  sol  is  a  dichroic  liquid,  blood  red  by 
transmitted  light  and  muddy  red  by  reflected  light, 
which  contains  o-i  per  cent  of  copper  as  cuprous 
subhydroxide,  protected  by  a  combination  of  amino- 
acids,  which  per  se  have  a  very  low  physiological  action. 
The  solution  is  very  stable,  but  should  not  be  exposed 
unduly  to  the  action  of  air  or  light,  and  for  this  reason 
the  product  is  issued  in  hermetically  sealed  ampoules, 
each  containing  sufficient  for  one  injection. 

It  appears  to  be  of  use  in  some  cases  of  cancer,  and 
the  dissipation  of  a  nodule  in  a  patient  who  had 
previously  been  operated  on  for  scirrhus  of  the  right 
breast  (cancer)  is  reported.  Results  are  in  many  cases 
satisfactory,  particularly  in  the  initial  stages  of  the 
growth  and  in  preventing  recurrence  after  operation. 

1  D.  A.  Wood,  Brit.  Med.  Joufn.,  1919,  330. 


Where  pain  is  present,  great  relief  is  obtained  by  the 
intravenous  injection  of  colloidal  iodine.  If  any 
streptococcus  is  present,  injections  of  colloidal  man- 
ganese should  be  given  alternately  with  those  of  copper. 
In  some  cases  where  an  improvement  is  manifested,  but 
not  maintained,  injections  of  a  reducing  agent,  such  as 
pallamine  (colloidal  palladium)  or  intramine  may  be 
given  alternately  with  copper  or  manganese,  Inj  ections 
of  colloidal  copper  should  always  be  given  intramuscu- 
larly, preferably  in  gluteus  medius.  The  dose  is  3  cc. 
and  the  injection  is  preferably  given  on  the  first,  fourth, 
seventh,  and  twelfth  days  and  then  once  a  week. 
Treatment  should  be  continued  until  all  symptoms  have 
completely  disappeared,  after  which  one  injection  per 
month  should  be  continued  for  about  a  year. 

The  use  of  colloidal  copper  injected  intravenously 
can  aggravate  boils  if  administered  in  large  doses ; 
in  smaller  quantities  and  injected  intramuscularly  it 
has  the  opposite  effect,  but  is  far  inferior  to  colloidal 
manganese  for  this  purpose. 

In  malignant  disease  the  intramuscular  injection 
of  copper  has  proved  beneficial,  the  metal  having 
been  shown  to  be  present  in  the  growth  within  twenty- 
four  hours  of  the  injection.  Merchel  de  Gers  and 
others1  have  stated  that  colloidal  copper  exerts 
an  inhibitive  action  on  all  cell-metabolism  and  it 
has  been  used  extensively  on  the  Continent  in  the 
treatment  of  cancer.  In  this  connection,  it  is  impor- 
tant to  note  that  cases  of  cancer  in  which  copper 
can  be  shown  to  be  present  in  the  growth  are  certainly 
the  ones  which  are  most  amenable  to  treatment.  The 

1  Med.  Press,  1912,  II,  26  ;    1913,  I,  87. 


difficulty  lies  in  causing  the  copper  to  penetrate  to  the 
periphery  of  the  cancer. 

Pessaries  of  colloidal  copper  in  glyco-gelatin  have 
proved  serviceable  for  uterine  fibroids. 

Luton  l  refers  to  the  value  of  the  salts  of  copper  in 
tuberculosis  ;  its  various  forms  yield  more  or  less 
rapidly  to  the  treatment  when  begun  regularly.  The 
existence  of  high  fever  is  regarded  as  an  obstacle  to  the 

Colloidal  platinum  sol  has  been  extensively  used  in 
promoting  various  chemical  reactions.  It  appears  to 
be  too  powerful  for  use  in  medicine,  but  has  been 
employed  to  a  limited  extent  for  the  same  diseases  as 
colloidal  silver. 

Dr.  A.  G.  Auld  has  obtained  encouraging  results  with 
colloidal  platinum  in  case  of  pyrexia,  e.g.  subacute 
pleuritis  and  pneumonic  conditions  and  protracted 
paratyphoid  fever.  He  found  that  colloidal  silver 
acted  even  more  intensely  than  the  year-old  platinum 
colloid  previously  used,  and  as  it  is  less  drastic  it  is,  in 
every  way,  preferable. 

Colloid  palladium  oxide  has  been  applied  successfully 
in  the  treatment  of  obesity  by  injecting  it  hypoder- 
mically  into  the  fatty  areas.2 

Colloidal  palladium  is  a  reddish  liquid  of  a  peculiarly 
active  character 

A.  C.  King-Turner  3  has  used  colloidal  palladium 
(pallamine)  with  good  results  in  epilepsy,  the  results 
of  injecting  each  patient  intramuscularly  with  0-5  cc. 

1  Prov.  Med.,  Dec.,  1912. 

8  Brit.  Med.  Journ.,  1918,  I,  195. 

3  M.  Kauffmann,  Munch.  Media.  Wochenschr,  525,  1913. 


of  "  pallamine  "  at  intervals  of  three  days  being  most 
marked  and  encouraging.  To  cite  three  cases  : l 

"  H.  G.,  male,  aged  forty-five,  suffering  from  epilepsy 
and  of  doubtful  traumatic  history,  had  an  average  of  at 
least  four  fits  weekly.  These  fits  were  of  a  very  violent 
nature,  the  convulsion  stage  lasting  on  occasions  for 
an  hour,  followed  by  stupor,  confusion,  and  excitement. 
Since  the  three  injections,  only  one  fit  has  occurred  in  a 
fortnight,  and  that  of  a  mild  nature,  lasting  only  thirty 
seconds.  The  patient  feels  greatly  improved  in  general 
health,  is  less  morose,  more  conversant,  expressing 
himself  more  lucidly,  and  is  very  grateful  for  the 

M.  A.  L.,  female,  aged  fifty-three,  an  epileptic  of 
thirty  years'  standing,  with  an  average  of  six  fits  per 
week  of  a  very  violent  nature.  Since  injection,  three 
weeks  ago,  no  fit  has  occurred,  but  she  has  had  a  few 
sensations.  She  is  now  very  placid,  well  behaved,  and 
much  better  in  every  way. 

M.  A.,  female,  aged  sixteen,  congenital  epilepsy. 
She  had  seldom  less  than  three  or  four  fits  per  day. 
Since  injection,  three  weeks  ago,  only  four  fits  have 
occurred.  She  is  much  brighter,  greatly  improved  in 
general  health,  and  has  now  great  hopes  of  being  dis- 
charged from  the  institution,  recovered.  In  two  cases 
where  manganese  sol  was  injected  after  pallamine,  a 
fit  resulted,  showing  that  careful  selection  of  the 
appropriate  metal  is  necessary." 

Like  colloidal  platinum,  pallamine  is  a  very  powerful 
catalyst,  and  such  strongly  combined  organic  sub- 
stances as  nitro-benzol,  and  numerous  acids,  aldehydes, 

1  Brit.  Med.  Journ.,  1918,  II,  255. 


ketones,  diketones,  and  nitriles  are  readily  reduced  by 
passing  hydrogen  through  them,  if  a  little  colloidal 
palladium  is  present  and  the  products  are  kept  neutral 
by  the  addition  of  sodium  carbonate. 

Sols  which  are  not  normal  constituents  of  the  body, 
e.g.  mercury,  arsenic,  are  liable  to  be  toxic,  but  mercury 
is  less  toxic  than  arsenic,  as  it  has  less  affinity  for  nerve 
tissue,  and  the  colloidal  preparations  are  quite  unlikely 
to  be  dangerous  in  the  hands  of  medical  men.  It  is, 
of  course,  important  that  they  should  be  prescribed 
with  due  care  as,  otherwise,  oxidation  may  occur  where 
reduction  is  desired,  or  vice  versa,  but  the  risk  of 
serious  results  to  the  patients  is  far  less  than  when 
certain  crystalloid  remedies  or  tinctures,  etc.,  are  used. 

Colloidal  nickel  has  been  used  in  meningitis. 

Of  the  non-metal  elements,  the  most  widely  used  are 
iodine  and  sulphur. 

Colloidal  iodine  may  be  obtained  in  four  forms: 
(i)  aqueous,  and  (ii)  oil,  (in)  ointment,  and  (iv)  sup- 
positories with  gly co-gelatin  base.  The  aqueous  colloid 
(i  in  500)  contains  the  element  in  its  most  active  form, 
and  is  suitable  for  administration  in  all  cases  in  which 
iodine  or  an  iodide  is  indicated.  Its  action  is  more 
gradual,  but  more  certain,  than  that  of  iodides,  and 
there  is  complete  avoidance  of  "  iodism  "  and  nausea. 

The  whole  of  the  colloidal  iodine  is  absorbed, 
whereas  85  per  cent  or  more  of  the  ordinary  iodides 
administered  are  excreted  within  twenty-four  hours. 

When  injected  intravenously,  the  action  of  colloidal 
iodine  is  more  rapid,  and  as  much  as  300  c.cs.  has  been 
injected  with  impunity  in  cases  of  pyaemia,  and  also 
to  produce  softening  of  fibrous  tissue,  thus  showing 


its  absolute  non-toxicity.  In  itself,  colloidal  iodine  is 
only  slightly  parasitotropic  and  bacteriotropic,  but 
micro-organisms  are  very  greatly  influenced  by  its 
action,  and  it  greatly  increases  the  effect  of  a  subse- 
quently administered  remedy. 

Colloidal  iodine  is  also  indicated  in  syphilis  by  prior 
injection,  and  also  by  internal  administration,  and  in 
cancer  by  intravenous  injection. 

In  rheumatism,  a  piece  of  flannel  soaked  in  colloidal 
iodine  attached  to  the  positive  pole  of  a  battery  and 
applied  as  near  as  possible  to  the  affected  area  has  been 
successful.  It  has  also  been  used  beneficially  as  a 
spray  in  bronchial  and  nasal  catarrh  and  internally  in 
recovery  from  alcoholism. 

Colloidal  iodine  oil  (3  per  cent)  is  very  useful  for 
eczema  and  other  forms  of  affections  and  abnormal 
conditions  of  the  skin.  On  application,  the  iodine 
particles  penetrate  the  pores  of  the  skin  without  stain- 
ing the  epidermis,  the  latter  being  kept  supple  and 
soft  by  the  hydrocarbon  oil  in  which  the  colloidal 
iodine  is  exhibited  and  stabilised.  Thus,  the  staining 
and  hardening  effects  of  alcoholic  solutions  of  iodine, 
such  as  tincture  of  iodine,  are  avoided. 

In  some  cases  of  bad  chilblains1  colloidal  iodine 
oil  rubbed  in  four  or  five  times  a  day  caused  every 
trace  of  the  condition  to  disappear  in  four  days. 
Equally  valuable  is  this  colloid  in  severe  cases  of 
trench  feet  with  ulceration,  and  in  many  cases  of 
Charcot's  bedsores  which  are  so  troublesome  a  com- 
plication of  spinal  injuries  in  military  hospitals.  In 
the  earlier  inflammatory  stages  of  lupus  erythematosus, 

1  Brit.  Med.  /.,  May  12,  1917. 






o   ^ 


before  atrophy  has  supervened,  it  is  far  more  suitable 
than  the  ordinary  form  of  the  drug  because  of  the 
absence  of  irritation.  Similarly,  it  is  preferred  for 
internal  administration  in  the  later  stages  of  syphilis, 
because  there  need  be  no  fear  of  iodism.  Parasitic 
affections  show  a  striking  amenability  to  this  remedy. 
In  a  case  of  dhobie's  itch,  in  which  the  disease  had 
spread  from  the  groin  and  invaded  the  trunk,  legs,  and 
arms,  under  the  quite  painless  application  of  colloidal 
iodine  oil  the  extensive  lesions  all  cleared  up  in  three 
weeks  ;  with  ordinary  remedies,  the  case  would  un- 
doubtedly have  been  more  protracted,  and  the  treat- 
ment would  inevitably  have  put  the  patient  to  a  good 
deal  of  pain. 

Colloidal  sulphur  (i  per  cent)  has  proved  invaluable 
in  cases  where  there  is  a  deficiency  of  this  element  in 
the  system.  The  value  of  sulphur  has  long  been  known, 
but  the  forms  in  which  it  is  usually  administered  are 
crude.  It  has  been  necessary  to  employ  excessively 
large  doses  of  an  insoluble  form  of  sulphur  or  to 
administer  "  Harrogate  water,"  or  some  equivalent 
and  unpleasant  preparation  of  hydrogen  sulphide. 
There  is  little  doubt  that  an  insufficient  amount  of 
available  sulphur  in  the  system  impairs  the  action  of 
the  liver,  with  consequent  production  of  intestinal 
poisoning  (constipation,  headaches,  arthritis,  etc). 
Externally,  in  the  form  of  ordinary  sulphur  ointment, 
the  element  is  in  far  too  coarse  a  state  to  penetrate 
the  epidermis  efficiently,  whereas  in  the  colloidal  form 
it  does  so  readily.  Colloidal  sulphur  ointment  (5  per 
cent)  is  a  brown  paste  ;  when  this  is  rubbed  on  the 
skin  its  colour  rapidly  disappears  owing  to  the  penetra- 


tion  of  the  sulphur  into  the  skin,  the  colourless  disperse 
medium  remaining  behind.  This  marked  distinction 
between  the  behaviour  of  colloidal  and  ordinary 
sulphur  is  obvious  to  every  one  who  has  compared 

Colloidal  sulphur  is  extremely  active,  readily  com- 
bines with  protein,  and  is  entirely  absorbed  in  the 
stomach.  The  products  of  this  combination  are 
rapidly  taken  into  circulation,  and  those  parts  of  the 
organism  for  which  sulphur  is  necessary  are  thus 
supplied.  Ordinary  sulphur  is  not  absorbed  in  the 
stomach  at  all,  and  passes  practically  unchanged  into 
the  intestines. 

A  very  interesting  property  of  colloidal  sulphur  sol 
is  its  power — when  taken  internally — of  completely 
deodorising  the  faeces,  and  thus  acting  in  precisely  the 
reverse  manner  to  ordinary  sulphur.  The  importance 
of  this  in  phthisis,  malignant  disease,  etc.,  is  obvious. 
In  many  cases  of  rheumatism  and  neuritis,  and  even 
in  "  arthritis  deformans,"  relief  has  been  rapidly  ob- 
tained by  its  internal  administration.  In  acute  rheu- 
matism, the  intravenous  injection  of  colloidal  sulphur 
has  proved  beneficial. 

Colloidal  sulphur  baths  have  been  of  service  in 
rheumatic  conditions  and  skin  affections.  The  colloidal 
sulphur  content  in  the  bath  is  far  greater  than  that  of 
natural  sulphur  water,  and  as  the  bath  contains  no 
impurities  or  free  sulphuretted  hydrogen,  it  is  free  from 
the  many  objections  associated  with  the  use  of  natural 
sulphur  waters. 
Sir  Malcolm  Morris1  has  found  that  among  the 



affections  in  which  colloidal  sulphur  is  beneficial  are 
various  forms  of  acne  (including  acne  rosacea  and 
seborrhcea),  generalised  dermatitis,  acute  psoriasis, 
and  painful  fibrositis,  whether  of  connective  tissue,  of 
muscle,  or  of  joints.  Baths  medicated  with  this 
colloid  are,  in  his  experience,  at  once  soothing  and 
quickly  curative. 

Colloidal  sulphur  increases  tolerance  to  mercury  in 
syphilis  and  enhances  its  efficacy.  It  has  also  been 
recommended  for  use  by  subcutaneous  injection  in 

Sulphur  can  be  administered  as  a  simple  sulphur  sol 
or  as  a  complex  colloid,  di-ortho-amino-thio-benzene 
(intramine)  as  prepared  by  J.  E.  R.  McDonagh.  These 
differ  somewhat  in  their  action,  but  for  the  cases 
previously  mentioned  either  form  may  be  used. 

Colloidal  arsenic  (0-2  per  cent)  in  doses  of  2  cc.  has 
an  extraordinary  effect  in  pernicious  ansemia  and 
herpes  deformans. 

In  influenza,  Capitan 1  obtained  cures  in  50  per  cent 
of  otherwise  hopeless  cases  with  doses  6-9  cc.  of  colloidal 
arsenic  and  the  same  volume  of  colloidal  silver.  The 
colloidal  arsenic  contains  about  4  mgm.  per  cc.  of 
arsenic,  and  the  colloidal  silver  2  mgm.  per  cc.  of  silver, 
the  solutions  being  given  intramuscularly  or  intra- 
venously. The  number  of  injections  varied  according  to 
the  effects  produced,  from  3  or  4  to  6  or  7  in  prolonged 
cases.  In  very  severe  cases,  6  cc.  of  colloidal  arsenic 
and  3  cc.  of  silver  were  injected  intravenously  at  once, 
and  twelve  hours  later  the  same  dose  was  given 
intramuscularly.  The  dose  was  repeated  next  day  if 

1  Bull.  Acad.  de  mid.,  Par.,  1918,  3*  Ser.,  80,  388-93. 


the  patient's  state  remained  grave.  If  there  was 
obvious  improvement,  a  single  intramuscular  injection 
of  9  cc.  of  arsenic  and  6  cc.  of  silver  was  given.  Patients 
who  recovered  after  one  or  two  injections  showed  a 
complete  change  in  their  general  condition ;  the 
prostration,  coma,  and  delirium  disappeared,  the 
temperature  fell  rapidly  to  normal,  and  the  pneumonia 
resolved  without  delay.  Apart  from  a  little  headache 
and  nausea,  no  bad  effects  were  produced.  Intramus- 
cular injection  of  stannic  oxide  in  colloidal  suspension  is 
advocated  by  Netter,1  who  has  used  them  in  139  cases, 
92  of  whom  were  children  and  47  adults.  The  injections 
were  given  for  several  days  in  succession  and  appeared 
to  shorten  the  duration  of  the  disease,  diminish  its 
gravity,  and  reduce  the  mortality.  The  mechanism  of 
the  action  of  stannic  oxide  is  not  clear,  as  the  bacteri- 
cidal power  of  tin  is  much  less  than  that  of  silver, 
although  Netter  has  found  colloidal  silver  much  less 
effective  than  stannic  oxide  in  such  cases.  Witte  2 
recommends  the  rectal  injection  of  a  2  per  cent  solution 
of  collargol3  from  two  to  four  times  daily  as  long  as  the 
fever  lasts,  the  patient  being  given  10  cc.  in  each 
injection.  The  treatment  should  be  begun  as  early  as 
possible,  especially  in  the  age-period  in  which  the 
mortality  is  highest,  namely,  from  twenty  to  forty. 

The  simultaneous  presence  of  a  lipoid  or  colloidal 
protein  appears  to  be  essential  to  the  proper  reaction 
of  arsenic.  Thus,  salvarsan  per  se  has  little  action  on 
Spirochceta  pallida,  which  can  move  readily  for  some 

1  Netter,  A.,  Bull.  Acad.  de  mtd.,  Par.,  1918,  3e  Ser,  80,  427-36. 

2  Witte,  F.,  Deutsche  med.  Wochenschr.,  Berl.  u.  Leipz.,  1918,  44, 

3  Collargol  is  a  silver  sol. 


hours  in  a  solution  of  salvarsan.  Yet  the  introduction 
of  a  little  serum  or  digested  protein  will  cause  their 
immediate  death.  Organic  arsenic  compounds  cause 
rapid  sterilisation  of  the  blood  stream  and  disappear- 
ance of  spirochaetes,  but,  owing  to  rapid  elimination, 
the  arsenic  is  unable  to  reach  every  spirochaete  or  its 
spore,  and  it  is  for  this  reason  that  the  intramuscular 
or  subcutaneous  route  is  sometimes  chosen  as  giving 
slower  absorption  and  consequently  slower  elimination 
and  more  prolonged  action  (Harrison).  The  dis- 
advantage of  this  method  is  the  pain  usually  caused. 
Colloidal  arsenic  is  not  so  easily  eliminated  and  may 
therefore  be  administered  by  the  longer  route. 
Its  low  toxicity,  combined  with  the  small  dosage 
required,  reduces  the  risk  of  its  retention  to  a 

Colloidal  oxides  do  not  prove  to  be  so  satisfactory  as 
the  corresponding  metals,  though  Colloidal  alumina 
(gel)  (  Eng.  Pat.  104,  609)  has  shown  excellent  as- 
tringent effects  in  various  kinds  of  diarrhoea  and  is  less 
toxic  than  the  bismuth  compounds  usually  adminis- 
tered in  such  cases. 

Various  alkaloids  have  been  prepared  in  the  colloidal 
state  and  have  been  used  in  medicine.  The  colloidal 
state  is  the  ideal  condition  for  the  administration  of 
alkaloids ;  in  it  they  are  isotonic  with  the  colloidal 
protein  of  the  body  fluids,  and  until  this  condition  has 
been  reached  the  full  physiological  action  of  the  drug 
is  not  complete.  The  two  most  important  of  these 
alkaloids  are  quinine  and  cocaine.  In  the  usual 
quinine  solutions,  time  is  wasted  converting  the  alkaloid 
to  this  state  and  there  is  frequently  considerable  upset 


of  the  conditions  regulating  the  blood  and  tissue  cells. 
Thus,  when  an  acid  quinine  solution  is  injected  intra- 
venously, precipitation  at  first  occurs,  and  the  quinine 
is  rapidly  taken  up  again  by  the  serum  as  a  colloidal 
sol,  but,  in  this  process,  the  normal  condition  of  the 
serum  is  destroyed.  When  colloidal  quinine,  which  is 
faintly  alkaline,  is  injected,  no  precipitation  can  occur, 
and  consequently  there  is  no  upset  of  the  normal 
condition  of  the  blood. 

Colloidal  quinine  sol  appears  to  be  free  from  the  chief 
drawbacks  of  quinine  salts.  As  the  latter,  as  well  as 
the  colloid,  are  readily  decomposed  in  corpore,  much 
more  research  is  required  before  much  can  be  said  as  to 
the  real  action  of  quinine.  Curiously,  colloidal  quinine 
has  no  action  on  the  parasite  of  malaria.1 

Colloidal  cocaine  is  peculiarly  difficult  to  prepare 
and  little  is  therefore  known  of  its  value  as  a  local 

Colloidal  combinations.  The  colloidal  elements  have 
usually  been  employed  singly.  This  is  important 
as  the  improper  combination  of  colloidal  sols  may 
result  either  in  an  inert  substance  or  in  the  production 
of  conditions  precisely  the  opposite  of  what  is  intended. 
For  instance,  A.  C.  King-Turner 2  has  found  that 
whilst  the  administration  of  colloidal  palladium  is 
helpful  in  epilepsy,  yet  subsequent  administration  of 
colloidal  manganese  induced  further  fits.  On  the  other 
hand,  suitable  mixtures  of  colloidal  elements  have 
great  possibilities,  which  are,  as  yet,  only  dimly  realised. 
For  instance,  a  mixture  of  colloidal  manganese  and 
iron  can  be  prepared  in  an  entirely  stable  form,  and 

1  Stroud,  Lancet,  1917,  II,  911.          *  See  pp.  97,  98. 


whilst  the  therapeutic  properties  of  such  a  mixture 
have  not  been  thoroughly  ascertained,  it  appears  that 
it  not  only  possesses  the  remarkable  properties  of 
colloidal  manganese  and  iron,  when  administered 
separately,  but  also  has  an  additional  effect,  the  nature 
of  which  requires  further  investigation. 

Complex  colloids,  such  as  gelatin,  gum-acacia  or  the 
protein  colloids,  are  injected  intravenously  in  cases 
where  it  is  desired  to  prevent  undue  loss  of  the  saline 
constituents  of  the  serum.  Such  colloids  adsorb  these 
crystalloids,  retaining  them  in  the  blood-vessels, 
raising  the  osmotic  pressure,  expelling  the  toxins  and 
generally  reducing  the  effects  of  shock.  After  severe 
haemorrhage,  both  the  colloidal  and  the  crystalloidal 
constituents  are  deficient,  and  an  injection  of  a  complex 
colloid  mixed  with  a  hypertonic  saline  solution  is  the 
most  efficacious  restorative.  If  the  saline  is  adminis- 
tered alone,  much  of  it  is  rapidly  excreted  and  lost. 
The  simultaneous  introduction  of  a  suitable  colloid 
ensures  the  adsorption  of  the  saline  matter  and  ensures 
its  efficacy.  Under  normal  conditions,  there  appears 
to  be  a  considerable  proportion  of  a  crystal-colloidal 
complex  in  the  body-fluids  and  for  the  retention  of 
health  a  sensitive  or  labile  equilibrium  between  the 
crystalloid  and  colloidal  contents  must,  therefore,  be 



THE  form  in  which  colloidal  sols  are  employed  has, 
naturally,  a  considerable  influence  on  their  effect. 
Several  German  preparations,  placed  on  the  market  by 
British  merchants,  have  given  disappointing  results 
because  those  physicians  who  employed  them  were 
insufficiently  well  acquainted  with  the  nature  of 
colloidal  sols.  Thus,  for  the  purposes  of  ordinary 
chemical  experiments,  sols  which  have  been  evaporated 
to  dryness  and  redissolved  in  water  immediately  before 
use  are  often  convenient,  but  for  the  much  more  severe 
conditions  of  medical  use  such  dried  sols  have  proved 

Again,  it  is  comparatively  easy  to  prepare  sols 
which  will  meet  the  ordinary  requirements  of  the 
chemical  lecturer,  but  such  crude  preparations  are 
usually  too  unstable  for  medical  purposes,  or  their 
stabilising  agent  or  other  constituents  bring  about  un- 
desirable complications  in  the  patient.  It  is,  therefore, 
of  the  greatest  importance  that  the  colloids  used  by 
physicians  should  be  prepared  with  special  skill  and 
care.  Many  samples  which  have  been  examined  show 
great  variations  according  to  the  sources  from  which 
they  have  been  obtained,  but  it  is  satisfactory  to  be 
able  to  state  that  the  preparations  to  which  special 



reference  has  been  made  in  this  volume  have  invariably 
proved  satisfactory  when  tested. 

There  is,  in  some  quarters,  an  idea  that  colloidal  sols 
are  too  unstable  to  be  of  real  value  in  pharmacy 
This  is  undoubtedly  true  of  the  crude  preparations 
made  by  those  who  have  not  the  necessary  knowledge 
and  skill,  but  it  is  emphatically  false  when  applied 
to  the  preparations  to  which  reference  has  already 
been  made. 

There  is  also  a  disposition  on  the  part  of  a  small 
number  of  recent  writers  to  confuse  ideas  of  the  differ- 
ence between  colloidal  elements  and  complex  organic 
compounds  which  may  be  used  either  in  a  colloidal 
state  or  in  the  form  of  a  true  solution.  This  is  an 
unfortunate  attitude,  as  there  is  no  necessary  in- 
compatibility between  the  two  classes  of  remedies. 
The  excellent  work  of  Ehrlich  and  his  associates  has 
had  most  remarkable  results.  It  has  clearly  shown  a 
line  of  attack  which  is  likely  to  prove  of  still  further 
value  in  the  conquest  of  syphilis  and  allied  diseases. 
On  the  other  hand,  it  cannot  be  denied  that  the  use  of 
arsenic  in  a  highly  poisonous  form  in  association  with 
an  organic  complex  which  is  intended  to  neutralise  its 
toxic  action  is  fraught  with  risks  which,  at  present, 
appear  to  be  much  greater  than  the  use  of  colloidal 
elements  of  very  low  toxicity. 

One  unfortunate  result  of  the  use  of  improperly  made 
colloidal  sols  has  been  the  publication  of  a  few  state- 
ments in  which  the  use  of  colloidal  sols  as  remedies  is 
condemned  in  general  terms.  If  the  origin  of  these 
statements  is  traced,  it  will  be  found  that  they  have 
been  made  by  those  who  have  insufficient  knowledge 


of  colloids  and  have  not  made  the  necessary  tests 
before  jumping  to  conclusions,  or  they  relate  to  colloidal 
sols  of  low  activity,  or  to  those  which  are  not  isotonic 
with  serum  and  other  body-fluids. 

Obviously,  any  conclusions  based  on  such  imperfect 
data  should  be  regarded  with  grave  suspicion  ;  they 
are  certainly  inapplicable  to  the  colloids,  mentioned  in 
the  foregoing  pages,  which  have  been  used  with  such 
highly  satisfactory  results. 

No  one  with  sufficient  knowledge  of  colloidal  sub- 
stances would  claim  that  all  drugs  should  be  adminis- 
tered solely  in  this  form.  There  are,  in  fact,  many 
crystalline  compounds  which  are  invaluable  for  special 
purposes.  Thus,  there  is,  in  health,  a  definite  equi- 
librium between  the  saline  (or  crystalloid)  and  the 
colloidal  content  of  the  body-fluids  which  must  be 
restored  when  it  has  been  disturbed  as  the  result  of 
wounds  or  some  bacterial  or  other  disease-producing 
agency.  Under  normal  conditions,  the  cells  and  serum 
are  colloidal  sols  which  retain  07  to  0^9  per  cent  of 
crystalloid  or  saline  matter.1  When  the  saline  content 
is  reduced  below  the  lower  of  the  limits  just  mentioned, 
the  administration  of  a  hypertonic  crystalloid  solution 
is  usually  indicated.  If,  on  the  contrary,  an  excessive 
amount  of  colloidal  sol  is  present,  the  appropriate 
remedy  may  consist  either  (i)  in  raising  the  concentra- 
tion of  the  crystalloids  by  the  administration  of  a 
saline,  or  (ii)  in  precipitating  the  foreign  colloid  by 
means  of  another  colloidal  sol  of  the  opposite  electric 
sign.  The  use  of  salines  is  well  known,  but  the  dis- 
covery of  artificially  prepared  colloids  which  are  stable 

1  B.  Moore,  Nature,  1919,  131. 


when  in  the  human  organism  is,  however,  so  recent  and 
the  results  obtained  from  their  administration  are  so 
remarkable  that  it  seems  desirable  in  the  interests  of  all 
that  their  general  characteristics  should  be  set  out 
briefly  and  clearly  in  order  that  still  further  progress 
may  be  made  in  the  utilisation  of  colloids  both  in 
health  and  disease. 


Abscesses,  93,  95 
Acid,  amino,  60,  89 

—  carbolic,  67,  68 

—  gallic,  25 

—  lysalbic,  7 

—  nucleinic,  28 

—  protalbic,  7 

—  tannic,  25 

Acne  of  the  face  and  hands,  83, 

"  Activated  sludge  "  process,  31, 


Activity  of  sols,  57 
Adsorption,  selective,  2,  3,  107 
Agar,  12,  13,  70,  71 
Agglutination,  15 
Agglutinins,  39,  40,  41 
Air,  action  of,  at  seaside,  3 1 
Albumen,  7,  12,  23,  25,  26,  43, 

46,  81 

Alcoholism,  100 
Algae,  unicellular,  13 
Alimentary  tract,  28,  42 
Alkaloids,  colloidal,  105 
Alumina,  colloidal,  105 
Aluminium,  colloidal,  73 

—  hydroxide,  colloidal,  1 2 
Alveolaris,  pyrorrhoea,  86 
Amino-acids,  60,  89 
Amoebae,  13 

Anaemia,  78,  88,  103 
Angina,  Vincent's,  83 
Aniline  blue,  colloidal,  12 
Animal  fluids,  21 

—  organisms,  1 3 

—  structure,  2 
Ani,  pruritis,  85 
Antimony,  colloidal,  73,  89-90 

—  sulphide,  colloidal,  1 2 
Anti-toxins,  nature  of,  39,  40 
Appendicitis,  suppurative,  83 
Aqueous  phase,  46 
Argyrol,  94 

Arrhenius,  S.,  41 
Arsenic,  49,  109 

—  colloidal,  99,  103-105 

Arsenic,  sulphide,  colloidal,  12 

Arsenious  acid,  colloidal,  73 

Arseno-benzene,  87 

Arthritis,  101,  102 

Assaying  sols,  56-66 

Asses'  milk,  22 

Assimilation,  2 

Atropine,  84 

Atrophy,  38,  101 

Auld,  A.  G.,  97 

Axillae,  bromidrosis  of,  83,  85 

Bacillus  coli  communis,  70,  71, 

—  tuberculosis,  7 1 

—  typhosus,  88 
Bacteria,  i,  17,  36 

—  action  of  agglutinins  on,  39, 

—  colloidal  nature  of,  15,  17,  68 

—  destruction  of,  38,  68 

—  penetration  -of  cell  walls  by, 

—  propagation  of,  38 

—  "  protection  "  of,  41 

—  sensitiveness  of,  39 
Bancroft,  35 

Baths,  medicated,  103 

—  sulphur,  102 

Bed  sores,  Charcot's,  100 

Bilharzia,  89 

Bismarck,  brown,  colloidal,  1 2 

Bismuth,  colloidal,  12,  73 

Black  background,  58 

Bladder,  disease  of,  28 

Blenorrhrea,  gonorrhosal,  94 

Blepharitis,  84 

Blood,  carbon  dioxide  in,  26 

—  corpuscles,  26,  27 

—  nature  of,  27 

—  oxygen  in,  26 

—  serum,  40,  5 ! 
Body  fluids,  44,  109 

colloidal  state  of,  37,  49 

—  viscosity  of,  2  5 
Boils,  83,  90,  91,  96 



Bordet,  J.,  41 

Boric  lotion,  94 

Bromidrosis  of  the  feet,  83,  85 

Brownian  movement,  5,  57 

Burns,  84 

Burton,  9,  10 

Buxton,  25 

Cadmium,  colloidal,  73 

—  sulphide,  colloidal,  12 
Cancer,  95,  96,  100 
Cantlie,  Sir  James,  83 
Capitan,  103 
Caramel,  13 

Carbolic  acid,  67,  68 
Carbon  dioxide  in  blood,  26 
Carbuncle,  91 
Casein,  7,  64,  8 1 

—  digestion  of,  23 

—  in  milk,  22 

Catalytic  action  of  colloids,  79 
Catarrh,  83,  86,  88,  100 
Cells,  action  of  salts  on,  24,  25, 

—  embryonic,  95 

—  growth  of,  25 

—  nature  of,  25 

—  reactions  in,  24 

—  selective  permeability  of,  24, 

—  structure  of,  2,  23 

—  synthetic,  23 
Cellulitis,  88 
Cellulose,  81 
Cerebro-spinal  fluid,  6 1 

—  meningitis,  86 

Cerium  hydroxide,  colloidal,  12 
Chadwick,  Sir  Edwin,  33,  34,  37 
Chambers,  23 
Charcot's  bed-sores,  100 
Charge,  electric,  on  a  sol,  9 
Cheese,  digestion  of,  23 
Chemical  action  and  electrical 

phenomena,  8 
Chilblains,  100 
Chloroform,  colloidal,  13 
Chromium  hydroxide,  colloidal, 


Cinchona  bark,  80 
Cleanliness,  importance  of,  33 
Cobalt,  colloidal,  73 
Cocaine,  colloidal,  76,  105,  106- 


Coccogenic  skin  disease,  89,  90 
Cod  liver  oil,  emulsions  of,  46 

Collins,  Sir  Wm.,  38 
Colloidal  metals,  electric  charge 
of,  70 

germicidal  power  of,  68,  73 

nature  of,  69 

—  sols,  precipitation  of,  13-15 
protection  of,  1 5 

—  particles,    action   of   electric 
current  on,  1 1 

activity  of,  1 8 

calculation      of      electric 

charge,  9 

double  electric  layer  of,  10 

electric  charge  on,  7,  12,  13 

oscillation  of,  5,  18 

rate  of  movement,  1 3 

size  of,  5,  20 

volume  and  surface  area, 


—  remedies,  76-107 

—  sols,  action  of  radiations  on, 

precipitation  of,  13-15 

protection  of,  1 5 

—  state,  denned,  4 
Colloidogens,  7 

Colloids,  absorption  spectra,  20 

—  accidental  use  of,  45 

—  action  of  air  on,  65 

alkalies  on,  78 

dust  on,  65 

heat  on,  65 

light  on,  65 

membranes  on,  43 

—  adsorption  of,  68 

—  advantages  for  internal  use, 

Colloid  and  crystalloid,  equi- 
librium between,  107 

Colloids  and  digestion,  2,  42- 

—  and     solutions,     distinction 
between,  16 

—  appearance  of,  57 

—  characteristics  of,  7 

—  coagulation  of,  50 

—  colour  of,  19 

—  colour,  variations  of,  20 

—  complex,  107 

—  determination  of  activity, 

—  dosing  of,  53,  79 

—  effect  of  serum  on,  65-66 
time  on,  65 

—  equilibrium  of,  5  5 


Colloids,  German,  50 

—  hydrolysis  of,  43 

—  injection  of,  34,   54,  80,  85, 
88,  91,  93,  96,  97,  99,   103, 
104,  1 06 

—  intensity  of  reaction,  78 

—  mixed,  106 

—  nature  of,  1-20 

—  preparation  of,  51,  54 

—  properties  of,  1-20 

—  protection  of,  5 1 

—  protein,  107 

—  settling  time  of,  65 

—  stabilising,  5  5 

—  stability  of,  50,  51,  55,  66 

—  under  ultra-microscope,  57 

—  unstable,  51,  54,  60,  108 
Colour  of  colloids,  19 
Common  salt  as  colloid,  6 
Compounds,  dissociation  of,  9 
Condensation,  53,  54 
Congenital  epilepsy,  98 
Conjunctiva,  82 

—  oedematus,  bulbar,  94 
Conjunctivitis,  gonorrhoeal,  83 

—  phlyctenular,  83 
Constipation,  101 

Copper,  colloidal,  12,  73,  81,  95- 

—  hydroxide,  colloidal,  12 
Cow's  milk,  21,  22 
Corneal  ulceration,  94 
Corrosive  sublimate,  72 
Cretinism,  78 

Crookes,  Henry,  52,  68,  69,  70, 

73.  74 

Crystalloids  under  ultra-micro- 
scope, 58 

—  and  colloids,  equilibrium  be- 
tween, 107 

Cuvette,  59 
Cystitis,  83,  86 

Dacryocystis,  84 

Deltas,  formation  of,  33 

Dermatitis,  85,  103 

Dextrin,  64 

Dhobie's  itch,  101 

Dialysis,  n 

Diarrhoea,  105 

Diatoms,  colloidal,  13 

Diffusion,  n,  28 

Digestion  and  colloids,  2,  42-44 

—  nature  of,  26,  43 

Digestion  and  colloid  products, 
action  of  colloidal  iron  on,  89 

Dilute      solutions,      germicidal 
power  of,  69 

Diphtheria  toxin,  40 

Diplococcus,  71 

Dipsomania,  80 

Disease,  origin  of,  36,  37 

Disease-producing  organisms, 
evolution  of,  38 

Disinfectants,  colloidal,  67 

Disperse  phase,  4,  46 

Dispersion  medium,  4,  51 

—  power  of  soaps,  34 
Dissociation  of  salts,  9 
Donnan,  43 

Double  electric  layer,  10 
Drainage,  importance  of,  33 
Drugs,  action  of,  79 

—  dose  and  effect,  47 

—  erroneous  results  from  intro- 

duction of,  17 

—  ionisation  of,  79 
Dyes,  7 
Dysentery,  83 

Ear  affections,  83 
Ebonite,  electrification  of,  8 
Eczema,  83,  85,  89,  90,  100 
Ehrlich,  49,  109 

Electricity,  influence  on  animal 
organisms,  13 

—  use  of,  as  a  remedy,  1 3 
Electrification  of  colloidal  par- 
ticles, 7 

Electrolytes,  6,  7,  10 
Electronegative  colloids,  7 
Electropositive  colloids,  7 
Embrocations,  46 
Emetics,  47 
Emulsifying  agents,  46 
Emulsion,  39,  46 
Emulsoids,  6,  23,  25 
Endoscope,  86 
Enzymes,  17,  42,  78 
Eosin,  colloidal,  12 

—  solution,  62 
Epiditymitis,  83 
Epilepsy,  97,  98,  106 
Erysipelas,  88 
Erythematous  lupus,  100 
Eustachian  tubes,  86 
Faeces,  deodorising,  102 
Faraday,  80 



Ferments,  42 

Ferric  hydroxide  sols,  12,  27 

Fever,  paratyphoid,  97 

Fibrositis,  103 

Fibrous  tissue,  99 

Field  and  Teague,  40 

Fish-agar,  74 

Fluid,  cerebro-spinal,  61 

—  gland,  78 

—  thyroid,  78 
Follicular  tonsilitis,  83 
Folliculitis,  acute,  90 
Foot-and-mouth  disease, 
Formalin,  68 

Formic  aldehyde,  54 
Fuchsine,  colloidal,  54 
Furunculosis,  90 

Gallic  acid,  25 

Galvanotropism,  25 

Garnet,  81 

Gelatin,  4,  6,  13,  21,  22,  23,  24, 

28,  39,  64,  107 
Gels,  denned,  14 

—  formation  of,  14 

—  haemolysis  of,  27 
Germicides,  colloidal,  67 
Gland,  prostate,  86 
Glands,  78 

Glass,  electrification  of,  8 

Gleet,  86 

Globulin,  colloidal,  12 

Glue,  64 

Gluteus  medius,  96 

Glyco-gelatin,  97 

Glycogen,  48 

Glycophosphates,  48 

Gold  chloride,  54 

—  colloidal,  9,  19,  54,  73,  80-8 1 

—  metallic,  3 

—  number  of  sols,  63-65 
Gonococcal  urethritis,  90 
Gonococcus,  71 
Gonorrhoea,  83 
Gonorrhoea!  blenorrhoea,  94 

—  conjunctivitis,  83 

—  ophthalmia,  83,  93 

—  prostatic  gleet,  86 
Graham,  Thomas,  3,  16 
Granulama  pupendi,  90 
Graphite,  colloidal,  73 
Gum  acacia,  21,  24,  107 

—  arabic,  2 1 ,  64 

Gutbier  and  Resenschack,  20 

Habgood,  W.,  90 

Haematin,  16 

Haemoglobin,  12,  26,  27,  43,  88, 


Haemolysis,  27 
Haemorrhage,  107 
Haemorrhoids,  85 
Harrison,  105 
"  Harrogate  water,"  101 
Headaches,  101 
Henri, 26 

Herpes  deformans,  103 
Hewin  and  Mayen,  19 
Hewlett,  R.  Tanner,  71 
Histone,  25 

Hoffmann,  violet,  colloidal,  12 
Homoepathists,  53 
Hovell,  J.  Mark,  86 
Human  milk,  21,  22 

—  system,  action  of  radiations 
on,  19 

Hydrogen  sulphide,  78 
Hydrolysis,  53,  54,  76 
Hygienic  uses  of  colloids,  29 
Hypertonic  salt  solution,    107, 

Impetigo,  83,  90,  92 

Indigestion,  44 

Indigo,  colloidal,  12 

Influenza,  86,  103 

Injection  of  colloids,  34,  54,  80, 

85,  87,  88,  91,  93,  96,  97,  99. 

103,  104,  106 
Interstitial  keratitis,  84 
Intestinal  troubles,  83 
Intramine,  90,  103 
Iodine,  colloidal,  13,  18,  56,  65, 

76,  77,  87,  96,  99-101 

—  in  alcohol,  18 

—  in  animal  organisms,  78 

—  oil,  colloidal,  99-101 

—  stainless,  77 

—  tinctures,  77 

"  lodism,"  99,  101 

lonisation  of  drugs,  76,  79 

Ionised  state,  79 

Ions,  79 

Iridium,  colloidal,  73 

Iron  as  protein  compound,  88 

—  carbonate,  objections  to  use 
of,  89 

—  colloidal,  12,  77,  88,  89,  106 

—  compounds,  89 

—  hydroxide,  colloidal,  1 2 



Iron  in  animal  organisms,  78 

—  in  human  organism,  88 

—  solutions  as  remedies,  77 
Isinglass,  64 

Itch,  Dhobie's,  101 

Jones,  B.  Seymour,  86 

Kala-Azar,  90 
Keratitis,  interstitial,  84 
King-Turner,  A.  C.,  97,  106 
Kirk,  E.  W.,  90 

Lact-albumen,  in  milk,  21,  22 
Lead,  colloidal,  12,  73 
Lecithin,  13,  48 
Leishmonnoris,  89 
Lesions,  85,  93,  101 
Leucorrhoea,  86 
Levinson,  W.  E.,  90 
Linder  and  Picton,  1 2 
Liniments,  46 
Lipoids,  87,  104 
Lister,  36 
Living  organisms,  2 

—  and  dead  organisms,  differ- 
ence in  action,  1 6,  17 

Livingstone,  Dr.  McFarland,  93, 


Lottermoser,  15 
Lupus  erythematosus,  100 
Luton,  97 
Lysalbic  acid,  7 

McDonagh,  J.  E.  R.,  87, 91, 103 
MacLeod,  C.  E.  A.,  83 
MacMunn,  J.,  86 
Magdalene  blue,  colloidal,  1 2 
Magnesium,  colloidal,  73 
Malaria,  88,  106 
Malignant  disease,  102 
Manganese,  colloidal,  90-95,  96, 

98,  106 

Mastic,  colloidal,  1 3 
Mayen,  19 

Mayer,  Schaffer  and  Terroine,  20 
Medical  possibilities  of  colloids, 

50-52,  1 8 
Medicine,  use  of  colloids  in,  18, 

45,  52 
Membranes,  permeability  of,  2, 

3,  ii,  17,  24,  43 
Meningitis,    cerebro-spinal,    86, 


Merchal  de  Gers,  96 
Mercury  chloride,  78 
colloidal,  73 

—  colloidal,  12,  70,  71,  73,  76, 
80,  86-88,  89 

—  compounds,  47,  77 

—  cyanide,  colloidal,  73 

—  ointment,  84 
Metabolism,  96 

Metals,  colloidal,  activity  of,  79 

catalytic  action  of,  79 

effect  of,  on  blood,  79 

germicidal  power  of,  69 

use  of,  77 

Methylene  violet,  colloidal,  12 
Micrococcus  catarrhalis,  88 
Micro-organisms     and     disease, 


Migration  of  particles  to  elec- 
trodes, n,  15 
Milk,  asses',  22 

—  coagulation  of,  47 

—  cows',  21,  22 

—  human,  21,  22 

—  lime  water  in,  22 

—  protective  colloids  in,  21,  22 
Miller,  25 

Molybdene  blue,  colloidal,  12 
Moore,  no 

—  and  Roaf,  2 

Morris,  Sir  Malcolm,  85,  91,  93, 


Mud,  precipitation  of,  33 
Mustard  gas,  91 

Nanes,  25 

Nasal  catarrh,  83,  86,  100 

Nausea,  99 

Necrosis,  82 

Nervous  diseases,  phosphorus  in, 


Netter,  104 
Neuritis,  102 
Nickel,  colloidal,  99 
Nucleinic  acid,  28 
Nutrient  broth,  70,  72 

—  gelatin,  73 

Obesity,  97 

(Edema  of  the  face,  91 

QEdematus  bulbar  conjunctiva. 


Oil  emulsions,  1 3 
Ophthalmia,  gonorrhceal,  83,  93 

—  purulent,  84 


Organisms,  animal,  13 

—  living  and  dead,  43 

—  structure  of,  2 

—  vegetable,  1 3 
Ostwald,  Wolfgang,  6,  20,  26 
Otitis  media,  83 

Oxides,  colloidal,  105 
Oxygen  in  blood,  26 
Ozone,  31 

Paal,  95 

Palladium,  colloidal,  73,  76,  96, 

97-99,  1 06 

Parasitic  affections,  101 
Paratyphoid  fever,  97 
Parchment  as  a  membrane,  3,  16 
Pellicle,  26 
Pepsin,  47 
Peptisation,  54 
Peptones,  7,  16 
Perineal  eczema,  85 
Permeability,  selective,  2,  3,  n, 


Perrin,  25 

Petroleum,  emulsions  of,  46 

Phenol,  67,  68 

Phlyctenular  conjunctivitis,  83 

Phosphorus  in   the   animal   or- 
ganism, 78 
—  nervous  diseases,  48 

Phthisis,  1 02 

Picton,  12 

Piles.     See  Haemorrhoids 

Platinum  black,  79 

—  colloidal,  12,  73,  79,  97 
Pleuritis,  97 
Pneumococcus,  88 
Pneumonia,  104 
Podophyllin,  tincture  of,  45 
Poison  and  reactions  of  metallic 

sols,  42 

Poisoning,  42,  78 
Preparation  of  colloidal  sols,  53- 


Prostatic  gleet,  gonorrhoeal,  86 
Protalbic  acid,  7 
Protalbumoses,  43 
Protected  colloids,  1 5 
Proteins,  60,  87,  102,  104,  105 

—  colloidal,  107 
Protoplasm,  2,  23,  24,  25 
Pruritis  ani,  85 
Prussic  acid,  78 
Psoriasis,  103 
Puerperal  septicaemia,  85 

Pupendi,  granulama,  90 
Purgatives,  47 
Purulent  ophthalmia,  84 
Pus,  94 

—  cells,  71 
Pustular,  eczema,  83 
Pyaemia,  99 

Pyorrhoea  alveolaris  ,86 
Pyrexia,  97 
Pyrogenic  cocci,  88 

Quincke  and  Helmholtz,  10 
Quinine,  colloidal,  76,  105,  106 

—  disulphate,  62 

—  hydrochloride,  80 
Quinsies,  86 

Rachlmann,  25 

Radiations,  action  of,  on  sols,  19 
Rahe,  25 
Rayleigh,  19 
Rennet,  22,  47 
Resenschack,  20 
Resin,  colloidal,  13 
Rheumatism,  78,  100,  102 
Rhinitis,  86 
Rhodium,  colloidal,  73 
Rigg's  disease,  86 
Ringworm  of  the  body,  83 
Roaf,  2 

Roe,  A.  Legge,  83 
Rosaniline  hydrochloride,    col- 
loidal, 12 

Saline  matter  in  the  organism, 
107,  109 

—  solutions,  use  of,  107,  109 
Salt,  action  on  colloids,  43 

—  decomposition  of,  9 

—  water,  electrolytes  in,  3  3 
Salvarsan,  104,  105 

S  chaffer,  20 

Schlcesing,  33 

Scirrhus,  95 

Scopolamine,  84 

Seborrhoeic  eczema,  90 

Selective  permeability,  2,  3,  u, 

17,  24,  43 

Selenium,  colloidal,  13,  73 
Semi-colloids,  7 
Septicaemia,  83,  85,  86 
Septic  tonsilitis,  83 
Serum,  43,  51,  54,  107 

—  action  on  colloids,  65,  66 

—  immune,  39 



Serum,  syphilitic,  60 
Settling,  time  of,  65 
Sewage,  29-32 

—  bacterial  treatment  of,  32 

—  nature  of,  30 

—  precipitation  of  colloids  in,  3 1 

—  purification  of,  30 

—  sludge,  coagulation  of,  32 

nature  of,  32 

Shellac,  colloidal,  13 
Sherrer,  T.,  81 

Shingles,  86 

Shock,  107 

Silicic  acid,  colloidal,  12,  13,  64, 


Silk,  electrification  of,  7 
Silver  bromide,  colloidal,  12 

—  chloride,  colloidal,  12 

—  colloidal,  9,  12,  56,  70,  71,  72, 
73.  75,  76,  77,  81-86,  103 

—  iodide,  colloidal,  1 2 

—  metal,  germicidal  power  of, 


—  nitrate,  84 

—  stainless,  77 
Simpson,  W.  J.,  71 

Sizes  of  colloidal  particles,  5 

Skey,  33 

Skin  disease,  coccogenic,  89,  90 

—  permeability  of,  1 9 
Soap,  5,  7,  29,  33-35 

—  action  of,  34 

—  hydrolysis  of,  3  5 

—  nature  of,  35 
"  Soil,"  38 

Sol,  defined,  4,  16 

Solids  with  liquid  properties,  6 

Soluble  prussian  blue,  colloidal, 


Sores,  soft,  83 
Spencer  Herbert,  38 
Spirochaeta  pallida,  104,  105 
Spring  catarrh,  83 
Sprue,  83 

Stability  of  colloids,  50,  51,  66 
"  Stability  number  "  of  colloids, 

64,  65 

Stannic  acid,  colloidal,  8 1 
—  oxide,  colloidal,  104 
Staphylococcus  pyogenes,  71,  91 
Starch,  colloidal,  13,  64 
Stebbing,  20 
Streak  cultures,  70,  71 
Streptococci,  71,  96 
Sulphur  baths,  102,  103 

Sulphur  colloidal,    13,    54,    55, 
73,  76,  101-103 

—  in  the  animal  organism,  78 

—  ointment,  101 
Suppuration,  chronic,  83 
Suppurative  appendicitis,  83 
Suspensions  and  colloids,  differ- 
ence between,  16 

—  properties  of,  1 5 
Suspensoid  particles,  6 
Svedburg,  20 
Syphilis,  60,  87,  100,  103 

Tannin,  25 

Tantalum,  colloidal,  73 
Teague,  40 
Terroine,  20 
Thompson,  19 
Thorium,  colloidal,  73 

—  hydroxide,  colloidal,  1 2 
Thyroid  fluid,  78 

Tin,  colloidal,  73 
Tinctures,  45 
Tinea  versicolor,  83 
Tin  oxide,  colloidal,  12 
Titanic  oxide,  colloidal,  12 
Tobacco  disease,  36 
Tolman  and  Vliet,  62 
Tonsilitis,  83,  86 
Toothache  95 
Toxaemia,  85 

Toxins,  action  of  electric  cur- 
rent on,  40 

—  decomposition,  39 

—  destruction  of,  68,  107 

—  diphtheria,  40 

—  nature  of,  15,  39,  40 
Trench  feet,  100 
Trituration,  53 
Tuberculosis,  97 
Tulloch,  W.  J.(  41 
Turbinates,  enlargements  of,  86 
Tyndall,  John,  61 
Tyndallmeter,  62 

Tyndall  phenomena,  61-63 

Ulcers,  various,  83,  84 
Ulcus  molle  serpiginosum,  90 
Ultra-microscope,  57 
Unsanitary  conditions,  effect  of, 


Urea,  28 

Urethritis,  gonococcal,  90 
Uric  acid,  protection  of,  2 
Urine,  27,  28 

120  INDEX 

Urticaria,  85 
Uterine  fibroids,  97 

Vaccine  injections,  91,  92 
Valsava's  inflation,  86 
Valuation  of  colloids,  57 
Vanadic  oxide,  colloidal,  1 2 
Vegetable  fluids,  21 
—  organisms,  1 3 
Vincent's  angina,  83 

Water,  purification  of,  29,  32-33 
Weimarn,  Von,  6 

Wells,  T.  H.  Anderson,  85 
Whooping-cough,  86 
Witte,  104 

Yellow  fever,  36 

Zinc,  colloidal,  73 

Zirconium  hydroxide,    colloidal, 


Zsigmondy,  20,  55,  58,  64 
Zymotic  diseases,  36,  38 


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